You are not wrong. He sounds like he sucks, no offince, but even so, he should be doing every thing to kiss your familys ass, for you. do you understand what i am saying. He is bad mojo. Loss him. You are in the right.
I think you are right. Family is very important and you say it yourself, not only are your mother and sister family, they are also you best friends. they know you really well, and maybe you should listen to them.
As for your boyfriend, well he’s been cheating on you and doesn’t treat you right. do you really want to be in a relationship with him? I don’t think that what you describe is a good, fulfilling, lasting relationship between two persons that are in love with each other.
Now, whatever you decided, your boyfriend and your family do not have to get along (even if it’s better if they do), but you shouldn’t be stuck in between them or have to choose between them. I think your boyfriend is wrong in asking you to choose sides and to treat you the way he does when you talk to your mother and sister.He has to learn to take responsibility for his mistakes and stop blaming everything on others.