I'm dating a couple and it's not going well, but the husband really doesn't want me to leave

I've been dating a couple for about 9 months now, about three months in, the wife decides to break up but the husband does not want to let me go. Two weeks later she apologizes and we get back together, but then she started getting doubts about wanting this for her life. We have been working on it and trying to make it better but it is still rocky and she believes she is possibly just monogamous. They are due to go for IVF soon but I am not sure the wife wants me to be a part of the family. I love them both and the husband wants me in his life (I have even tried to break up, but he begs me to stay) but I can see this turning out bad for me. Kind of like once the kid is born I will be irrelevant. I don't know what to do.

You already know what to do, because you tried to do it at least once before. You know this is a bad situation for you; otherwise you wouldn’t have tried to end things. You describe things as “rocky” and say you “can see this turning out bad” for you. You know.

IVF is difficult and stressful, and you’re probably right that things are not going to get better once that starts. You don’t need anyone else’s permission or agreement to break up. Let the husband know that this is just not an arrangement that you want to be part of. He can beg, he can cry, he can argue - but that doesn’t change the fact that you’re ending things.