Threads merged and edited.
My boyfriend is the kind of person who likes to help people, people open up to him and he likes being there for people. He just recently started texting my sister a good bit. I am 100% sure that he's not cheating on me or that he's into her. I know he's not. But when he texts her it really bothers me, and he doesn't see a problem with it because I can't give him a reason as to why it bothers me. I really don't know why it does. Hes getting my sister to open up to him, but he will not tell me anything they talk about, he promised her he wouldn't. That bugs me too, because usually we are like each other's diary, we just tell each other everything even if we told someone before we wouldn't. But in this situation he won't tell me and it really upsets me. He told me I was being irrational and until I could give him a reason he didn't see a problem with it, I don't know what to do.. Am I being irrational?