Danni, you might think you get on great with them now, but what about when you live together, and for example...his sister is resentful of you not paying your way, being in her way, using her bathroom...etc? It's not a holiday, living with other people, believe me. Do you have a job, so you can pay your way at least a little? Will your bf contribute towards the rest? Are they BOTH prepared of having a teenager living under their roof? What if it goes wrong? Do you have anything to fall back on? Do you have anywhere else to go? Relationships DO break up, no matter how old you are, and you have to be prepared to be totally on your own.