Yeah, real problem. Apparently children always take the last name of the parent, despite the descr_strat entry, so "Godfrey de Bouillon" ingame is "Godfrey de Boulogne". This has been a real problem, and the only work around is to give the dead father the last name of "de Bouillon", then it should work
Code:
character_record Eustaceii de Bouillon, male, age 85, dead, 20, never_a_leader
character_record Ida de Lorraine, female, age 75, dead, 5, never_a_leader
character_record de Bouillon, male, age 42, dead, 10, never_a_leader
character_record Beatrice, female, age 25, dead, never_a_leader
relative Eustaceii de Bouillon, Ida de Lorraine, Eustaceiii de Bouillon, Godfrey de Bouillon, Baldwin, end
relative Godfrey de Bouillon, Beatrice, end
I've had this problem with Scandinavian factions.