unless he is the head of a sovereign or formerly sovereign house doing that I,II,III, cognomen stuff is phony and pretentious. its just another way lower social class people try and fail to adopt the ways of the nobility. what if you have a girl? hes gonna name her Micheal wb the 5th? All the hip lower class people are naming their kids after multicultural ghetto and trailer park places like Brooklyn and Dakota. Thats trendy. its also trendy and cool to give your children multiple New age names like orange ocean Asia, or blue rainbow America. Another rtrtend that is cool among trendy lower class people is to give their kids names that used to be nicknames for greaseballs like Rocco. I guess they think it sounds tough and alternative. Usually even in noble families we switch names from generations and adopt new ones based on the matrilineal descent of our children. My father was August Raymond Marie D'Arenberg, and I was Jean after my grandfather..Jean Luc August Charles Raymond Marie Gaspard D'Arenberg. Gaspard, Melchior and Balthasar are usually the last of the first names of princes of the catholic nobility of europe..bc those were apparently the names of the three kings who visited Jesus in that order, so my younger brother was Damon Louis Melchor D'Arenberg and my older half sister is named Sophie Anunciata .......Gaspara of Bavaria nee Arenberg.
if your BF says having children is a dealbreaker if he cant name him William mw the 4th or whatever it is then you two probably have some other things to figure out. A Childs name is secondary to many other things. Whatever you do dont be pretentious with it bc if you do he will have to live with that pretension. and by most social standards unless you two were married in a church, after the marriage being approved by the head of his family, the marriage would not be considered dynastic anyway..it would be morganatic and if you had a son he would not be the 2nd, 3rd, or 4th of anything.