@Joshua_Marshman FE4 includes: Claud and Sylvia, who are implied to be cousins by extra books, Lachesis, who says she can't love any man because they can't compare to her brother (and who is implied to be in love with her brother by the end), and a main plot driven by incest and can end in incest.
The weapon triangle exists in a sense, rather it being innate its done as skills. As for the other part, well Fire Emblem 4's whole moral of the story was Incest made the Final Boss :P
Basically, First cousins only for 'Real' Incest. Conquest just had a running theme of what makes you family, birthright or how your raised. Which was weird because the birthright side wasn't actually related despite it being their whole pitch
@Bryce_Adams as an old song lyrics:
In Trinidad there was a family
With much confusion as you will see
It was a mama and a papa, and a boy who was grown
Who wanted to marry and have a wife of his own
It's totally fine, the relationships with your siblings all bring up how you're not actually related. You just grew with them and totally thought you were at least half-siblings until it's revealed your mother arrived already pregnant. Hooking up is normal after news like that. /sarcasm
