Dynastic succession ( Elective gavelkind, Tanistry, Eldership, or Seniority) may be harder to predict and control.More crucially, failed holy wars by dynasts will cause decadence to soar. Decadence: Large Muslim dynasties risk becoming decadent, if dynasts are your vassals and your realm is the biggest in your dynasty.Inbreeding: You might be careful to avoid marriages between first cousins, but AI rulers are not.

Dynastic Kinslayer: You will have fewer safe murder choices, and your heir is more likely to decide to kill someone of your dynasty.There are some potential downsides to having a large dynasty: Higher opinion (+5 same dynasty and more for each book you write about your dynasty).Loyalists on your council (with Conclave), who vote with you on most issues even without a favor.Holy orders will also be cheaper to hire. Each one controlled by your dynasty gives you (and all other count+ rulers of your dynasty) +2 monthly prestige and +1 monthly piety. More chances to control the Papacy and holy orders (with Sons of Abraham).It also helps directly in marriage acceptance and cardinal election. Dynasty Prestige, which gives your kids starting prestige.Safety under feudal elective, once you make all those kingdoms into de jure vassals of your empire.This also lets you productively press claims for kinswomen, as long as the title is not agnatic.

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.Easier alliances: Dynasty members are more willing to form non-aggression pacts and alliances.In a marriage between dynasts, neither you nor the AI needs to worry about whether the marriage is patrilineal vs matrilineal. With no children of your own, a single dynastic heir will inherit all your titles. With gavelkind, proper planning can still ensure that titles are not lost during inheritance.If you represent the senior branch of the entire dynasty, you may inherit from exhausted branches and even extinct cadet branches. If you are the eldest, you may inherit seniority titles.

Future consolidation of titles: With seniority or any elective succession, your heir may already have titles.

Having your dynasty hold many titles has significant benefits:

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