Everyone reacts differently, but children pick up and are often upset when there is family tension between partners past and present, it’s very stressful for them to try and walk the fine line whilst trying not to upset others. I’m in my second marriage now and have been for over 30years. My First husband has been married twice and divorced twice since then, with many short term partners in between. I never felt jealous of them, although l got the idea that some felt uncomfortable when l visited, such as collecting or dropping off my girls to their Dad, but most of them came to accept the situation without difficulty, as did my new husband of them. It was never a problem for family gatherings, no animosity whatsoever.
TBH, you do sound quite insecure in your new relationship, how do you expect to move forward and be happy if you insist on being so suspicious and jealous about your partners Past?