so i dont want to make it seem like my sister has been the only person in the wrong. but i think explaining the situation will give a better picture of the situation.

so basically my boyfriend and sister seemed to get along in the beginning until my bf started being petty. so it all started from me being on facetime with my sister, he overheard that she wasnt letting me borrow her headphones and once she left the room he said shes disrespectful and will give her some words. i told him to leave it and he continued to message her anyway and say really nasty things that were just uncalled for, such as ,,hope you get raped and your dad beats you and you should respect your sister''. this really upset me and he never apologised. my sister obviously replied back to him and was extremely upset over it and so was i. i was dumb to have never made him apologise and was doing the apologising to both of them. then the second situation he messaged my sister by logging into my facebook account after me and him had an argument and started saying things like ''why have you been talking shit about me to your sister (as in me)''. which she hadnt been doing he just needed to take his anger out, and she replied with something quite bad, whic was along the lines of i hope your dad dies (his dad had cancer and has now passed away). i was shocked that she even said this, now i know my sister she is not an evil person and he really pushed her for her to say something like this, up til this point he always made remarks and digs and she ignored them till she finally said that. this of course sparked an argument between me and him too and i told him he should not have said anything to my sister as he is 4 years older than her and should have been the mature one and not said anyting in the first place. like what does he expect, he can say mean things and the other person will just sit there quiet. now i know what she said was out of order but when i mention what he had done was bad too he goes on the defense saying that i am comparing and what she said was worse. he eventually said he would apologise to her and would sort things with her but after his dad passing he wants nothing to do with her. this was brought up as he was supposed to be meeting with my mother this friday and says that he doesnt want to meet her due to the situation with my sister, i have met his family and sisters and they are sweet especially his mother and had met his dad before he passed also, however one thing that stuck with me when he mentioned this was that he said ''i want you to respect me and my family and tell her that i want nothing to do with her''..this just struck me because where was the respect for me and my family when he said those things to my sister..i know each family has their problems and issues and there would be another set of problems if i was to be with someone else, but i just think will it work between me and him if he doesnt get along with my sister and doesnt want to either, i just want some advice from someone experienced and tell me if im in over my head or it is something that i could work on