Sister Or Beloved

I would like to share something that does not give me peace and of course to hear your opinion. Let me say a little about me first. I am a 38-year-old woman and I live with a man without marriage. We both have one child from previous relationships. Mine is 14 and he is with us, and his is 19 and he is no longer with us. He lives separately with a girlfriend. We have been together for 4 years and we understand each other a lot, we speak freely on all topics. What weighs on me is something I realized recently. He told me about a girl he had wanted to be with for many years. She is the sister of his best friend. Because he was married for his brother and did not dare to do anything. The difference in age is not small. So he resigned himself to being just friends. After he divorced and slept with her before we met, he said she was the initiator and he took advantage. Ever since we met, she introduced me as a friend and we often communicate with them. Only now did she admit to me that she always said she felt like a sister. What hurt me the most was that he told me that he would never end this relationship, even if I didn't like it. Although I have not said such a thing. I think he still has feelings for her. She says she will never cheat on me, even though he can still be with her if she wants to. I also heard a comment from him that if you've been with someone once, you can't help but want to. although he can still be with her if he wants to. I also heard a comment from him that if you've been with someone once you can't help but want to. although he can still be with her if he wants to. I also heard a comment from him that if you've been with someone once you can't help but want to.