Is it right or wrong to feel this way ? Wht shud i do about it anyway :(?

Its not wrong to feel that way. That would bug me too, like alot. But i really think you should talk to him about it. If he gets mad, then thats pretty stupid cause he would be getting mad cause of your feelings, so are you sure you wanna be with someone like that?. And your sister should know that this bugs you, your sister should find her owns friends to talk you and leave your boyfriend alone. I wouldnt tell her how you feel cause she might tell him then he might get angery cause you didnt tell him yourself and think your hinding feelings from him. And if they you do tell him and he continues to talk about stuff with your sister i would say end it with him cause he obsously dosnent care about your feelings.