Need advice

My boyfriend and I have been dating for about a year and couple months and he's giving me a cold shoulder. This week for thanksgiving a cousin of mine (a female thats close to me) came home for the holidays. Now, my boyfriend is upset with me because he feels that I'd pick my family over him, he feels like he's holding me back from being with them. I DON'T feel this way AT ALL. What am I suppose to do or say? Why is he like this?