Why is his mother and rest of his family being so cold?

I had been dating this guy for 5 months, doesnt seem that long, but it was one of those rare situations where everything was just meant to be, and things just clicked from the beginning. His sister and I were really close and became friends. I see her on campus now, and she doesnt acknowlegde my existance she just stares and when I wave or say hi she avoids me. His dad also works at the school and I am always polite when I see him, but he doesnt say anything and he will just walk into the nearest room when he sees me or ignores me. His mother and I got really close, she treated me like a second daughter, she invited me over many times when my boyfriend was at school (he goes to school in a different state). I would see her atleast once every other week. My boyfriend broke up with me because he is so stressed out from school he cant manage a relationship too. He says his feelings havent changed one bit, and that he wants to stay in my life, just cant handel a relationship. After some time and talking I somewhat understand and am being mature about it all. I asked his mother if she wanted to go to coffee because we did all the time, and she said no very rudely. My boyfriend did tell me that it has been hard on his mom and sister, but I am very confused why they (especially his mom) would treat me so coldly? Its like the relationship was a smack in the face and now im being backhanded by the rest of his family.