This guide describes strategies for increasing the power of your dynasty through marriage. These techniques can be used to replace every royal bloodline and place dynasty members on every throne.
How does this benefit ME?
Having your dynasty hold many titles has significant benefits:
- Future consolidation of titles: With seniority or any elective succession, your heir may already have titles. If you are the eldest, you may inherit seniority titles. If you represent the senior branch of the entire dynasty, you may inherit from exhausted branches and even extinct cadet branches.
- With gavelkind, proper planning can still ensure that titles are not lost during inheritance. With no children of your own, a single dynastic heir will inherit all your titles.
- Easier marriage acceptance. In a marriage between dynasts, neither you nor the AI needs to worry about whether the marriage is patrilineal vs matrilineal.
- Easier alliances: Dynasty members are more willing to form non-aggression pacts and alliances.
- No need to land claimants: When pressing a claim on behalf of a dynast, they always become your vassal, so you don't need to give up precious demesne titles. This also lets you productively press claims for kinswomen, as long as the title is not agnatic.
- Safety under feudal elective, once you make all those kingdoms into de jure vassals of your empire.
- Dynasty Prestige, which gives your kids starting prestige. It also helps directly in marriage acceptance and cardinal election.
- More chances to control the Papacy and holy orders (with
Sons of Abraham). Each one controlled by your dynasty gives you (and all other count+ rulers of your dynasty) +2 monthly prestige and +1 monthly piety. Holy orders will also be cheaper to hire. - Loyalists on your council (with
Conclave), who vote with you on most issues even without a favor. - Higher opinion (+5 same dynasty and more for each book you write about your dynasty)
There are some potential downsides to having a large dynasty:
Dynastic Kinslayer: You will have fewer safe murder choices, and your heir is more likely to decide to kill someone of your dynasty.
Inbreeding: You might be careful to avoid marriages between first cousins, but AI rulers are not.
Decadence: Large Muslim dynasties risk becoming decadent, if dynasts are your vassals and your realm is the biggest in your dynasty. More crucially, failed holy wars by dynasts will cause decadence to soar.- Dynastic succession (Elective gavelkind, Tanistry, Eldership, or Seniority) may be harder to predict and control.
- With Feudal Elective succession, dynastic vassals have lower opinion of you than non-dynastic vassals. Dynastic vassals may also create a faction to demand a switch to gavelkind.
Avoiding gaining titles
While optional, it can be interesting to "play the marriage game" while remaining at count or duke level yourself.
You want somewhere that is not going to require a lot of micromanagement to rule and has little chance of being invaded. A remote location such as Iceland is relatively safe from invasion, but puts many rulers out of diplomatic range. A vassal duke in a strong kingdom or empire might be better.
Feudal elective succession is almost a must for this type of game, for a few reasons. First and foremost if your decided heir dies and/or screws himself or herself up to the point of unsuitability (Kinslayer, Arbitrary etc.) all on their own, you are not totally out of luck. Second, you will probably need to dodge some inheritances. This type of game is not about attempting to inherit France, rather it is about keeping France autonomous with your bloodline ruling it. And finally, you can select a female heir for more useful seduction options and matrilineal marriage options.
Children
Obviously in order to have a game in which your bloodline goes anywhere, you must have children to spare.
Fertility
Choose a spouse with high fertility: 
, 
, 
, or high diplomacy/stewardship education. You can also use Ruler Designer to give your first ruler these traits and/or extra base fertility.
The Seduction focus lets you have about as many children as you could want. Women can have about one child a year until age 45, and can either try to hide their affairs or hope rulers/heirs acknowledge children as theirs. Men can sire dozens of bastards.
Education
The following education types can help characters have many children, or remarry to have children with a second spouse:
| Type | Usefulness | |
|---|---|---|
|
Diplomacy |
Fertility boost, plot protection |
|
Martial |
Health boost, remarriage |
|
Stewardship |
Large fertility boost, helps spouse manage their demesne |
|
Intrigue |
Plot protection, remarriage (especially if they become their spouse's spymaster) |
|
Learning |
With |
Marriage
Now you have a brood of children, maybe with high intrigue or maybe with high fertility, ready to go out into the world and propagate your bloodline - these are specific strategies to get as advantageous a marriage as possible.
Males
By far the simplest way to get your dynasty going somewhere else is to simply regular marry your sons to landed females. Their children will be of your dynasty and the requirements for this are ridiculously low, if you are king-level or above then basically the sons which are heir and pretender (first 3) will be able to marry just about any landed female and this can easily be done just via the normal marriage rings.
Considerations
Your married male family members are by far the largest threat to your continued autonomy as if you marry your son to a Queen, she may suddenly decide she wants your land and presses his claim. Though this wouldn't end your game, it would certainly put a large damper on it. To that end, try to make sure that you are on good terms and/or they are unable to press or too far away to consider it. This should definitely not override potentially great opportunities, though; it is simply a consideration.
Females
Females are somewhat trickier as you can't simply marry them off; you need a matrilineal marriage and those are extremely difficult to do. Sometimes, you can get a matrilineal marriage that the AI will actually accept, but more often than not, you have to pull some tricks out. Here are some strategies specific to getting these marriages.
Matrilineal marriages
AI will only consider matrilineal marriages/betrothals if the woman/girl is your sister, daughter or granddaughter. For other women/girls in your court, you must invite heirs and have the marriage take place in your own court.
AI will usually accept matrilineal marriages as long as the man/boy is not in the top three for succession to the requestee's primary title. Thus, look for men and boys who are:
- Not in the court of their parent
- Junior heirs under gavelkind or elective gavelkind
- Heirs of heirs
- Younger children of rulers, if you can murder their older brothers
- Likely to win elections in the future, but currently not among the top 3 candidates
Considerations
Again, don't let Matrilineal marriages get in the way of marrying or betrothing your daughter to a really choice Heir. Sooner or later she'll have kids and you can start marrying cousins. In the meantime it's easier to make non-aggression pacts and alliances.
Heir
A very basic method to actually getting a matrilineal marriage that the AI will legitimately agree to is by using your Feudal Elective government to elect your daughter heir. You may of course use it to elect your niece/cousin/other heir, but the AI will not even recognize that they matter so it's your daughter or nothing. This makes it so when you open the marriage screen it's automatically matrilineal. Be warned though that this has very slim pickings regardless of how powerful you are or how great she is. You may however get lucky so it's worth looking at least.
The Meat
The meat of this strategy is fairly simple: find heirs that have claims and/or extreme daddy issues and invite them to your court. Once there, they cannot refuse a matrilineal marriage and you also have the added bonus of having them in your court so that you can protect them until they inherit. Be warned, however, that if they are extreme foreigners and/or unlikable, someone in your court will probably randomly decide to kill them and practically the entire court will back them, so you must be vigilant.
How to find these is fairly simple - when you go to your daughter's character screen you attempt to regular marry her, or at least open that screen. Sort by rank (crown) and scroll down past the landed guys and right below them will be princes. Hover over them to see if any of them are the heirs to the kingdom and if so take a look if they might be a possible option. Don't discount the guys below the princes as they may not have a minor title but be heirs to a large duchy. This is the easiest way, for the more complete way (these are only the ones that are willing to marry you which may not be half of them) you go to character finder (ruler:no, male:yes, married:no, greathouse:yes) and sort by rank, all the unlanded princes will be at the top underneath mayors/bishops.
To be willing to come to your court, they either need to absolutely hate their father, which is not unusual given the AI's seeming preference for bad ruling traits, or already have a claim which means they were alive and a pretender when the previous monarch before their father died.
It is actually relatively easy to get these guys as the combination of having a title claim and how much the AI loves to give itself arbitrary/cruel/etc, there is probably more than a 50% chance that any given unlanded heir will like you better, assuming you are a likable ruler yourself.
With the Conclave DLC, favors can be used to force an invite to your court, subject to some restrictions. This is the only way to invite claimants of other religions.
Remarriage
Whenever you marry off your children/eligible kin to someone with the intention of spreading your bloodline, mark their spouse as a 
person of special interest (right click -> star on the left). This will notify you if they die so that you can retrieve your guided dynasty missile for reuse somewhere else. If they are male and the heir and/or regent then definitely just leave them there for now and check up on them when their child grows up, if they are female definitely do everything in your power to get them back as there is only a certain window where they can have children.
Courtiers
You don't have to worry about marrying courtiers, but sometimes a Matrilineal marriage is just an easy way to get rid of somebody with a low opinion of you without going to the trouble of a plot. Again, it's good for getting hold of claims or boosting borderline opinions or making non-aggression pacts, as arranging marriages that benefit the courtier (ie giving them land) will make them a bit happier.
Don't worry too much about betrothing the children of courtiers, as they can't leave your court until they're adults anyway, and you can deal with them then.
Female matrilineal courtiers are basically bargaining chips to get the right people to come to court, without having to use your own bloodline to do it.
Muslim Rulers
As Muslim rulers you are limited to the Iqta inheritance and only until late game law change will you be able to have matrilinial marriage. However the unique inheritance also benefits you in that you will not lose any titles as Open Succession means that the most powerful son inherits all the titles, this also gives you great flexibility in determining your heir. If you do not have any legitimate sons then your most powerful brothers will inherit. If none of your sons have titles then it defaults into agnatic promigenture, which is fine for you.
After finding your ideal heir you need to look at how you can gain claims to titles that you so desire(and since women can't inherit until late game you will need to fight to seize these titles). Use the guide above to find female young fertile claimants with inheritable claims or look at titles in de jure page and find them. Marry them to your son. Invite as many as possible to your court and then land your son and heir. After that you can marry more female claimants to your son since he is Muslim and landed and thus get to have four wives(along with all their wonderful titles).
After which you would die and become your heir, then your oldest son/heir would inherit your titles and claims. Declare war when convenient and if done correctly, your son and heir would hold the duchy/kingdom and when you die, your realm will be sufficiently enlarged!
Conclusion
Don't despair if your carefully crafted bloodline replacement goes awry. A significant percentage of the time, some random bishop will methodically murder every one of the heirs that would have been of your dynasty and there is nothing you can do about it, really.
However, if it takes and you get past the first generation, then all of a sudden their interests are your interests, namely keeping your dynasty in power. Do what you can to help them out like putting down the inevitable rebellions and especially keep an eye out for usurpers. In addition, since the ruling dynasty is yours, if somehow the entire royal family dies out (mysteriously) then it will now look at your dynasty for possible inheritors.
Once you get to the 2nd generation, you are more or less free to worry about your other "colonies" as the bloodline is mostly established. Feel free to invite your own bloodline over to you like you did their grandfathers to make sure they get decent marriages and/or intermingle the royal families so that if they do lose the royal family, they will search others of your dynasty.
Hope this guide helps and feel free to post feedback on the discussion page.