HONESTLY YES I headcanon that Marth would ask his best friend Caeda if she could be a surrogate for him and Ren and that Caeda has a large presence in the kid's lives (they have multiple) and Marth would often bring her along to parties and stuff and he owes Caeda his life and skldfjskdfjf!!! As for their kids, their names would be Alfonse and Lucia!