Haha...this situation happens to me too. It for the starting, you will felt that your bf family does not like you as they didn'y talk to you. But no worries. When they are quite, does not means they don't like you.
My bf has a sister. So I'll talk to her. After talking to her, sometimes the parents will join and sometimes don't. But if join also talk not much.
You will adapt to it later.

If you ask them, they will only reply you En, ah, and etc...
If you want to be with your bf, you need to adapt to his family calture.
But that's when you with the family only.