Vampire Erotic Fiction Permanently turns in to vampire and becomes infertile at certain point

[Julia]

Hi everyone! Thanks in advance for the help! I can’t seem to find a book that I’ve read. It's an erotic fiction book about a girl dating (what turns out to be) a vampire. He has this family that lives in a huge mansion. He permanently will turn into a vampire at a certain point and will stop aging. They also become infertile then but he manages to get her pregnant before that with twins. They have this huge wedding at the mansion and then she turns into a vampire as well at some point. I can’t for the life of me think of what’s it’s called. It’s a series I think. Thanks in advance guys/girls/everyone :)