What should i do about my minor girlfreind's parents?

actually she's not my girlfriend... we where never allowed to date and i'm okay with that. the fact of the matter is that we do love each other. Her name is Nina and she's the greatest girl i've ever met. I'm 18 and she's 15, that's why we can't date and where both okay with that. Nina was conceived by her mom at the age of 15. Nina doesn't know her real father, but she's been raised by a man named Jess, for all intensive purpose's her dad. Jess and Nina's mother, Joyce, had there first child at 17 and got married after Joyce was pregnant. and now Jess and Joyce are scared to death i'm going to get Nina pregnant. But Nina's never even kissed a boy, and they thing she's going to elope with me. They think where going to make the same mistakes they did. On top of that Jess has these bad pride issues and i don't meet his standards. there saying we can't be friends and i'm scared. I love Nina to death... what should i do?