Caught boyfriend in bed with another woman. Why doesn’t she want him to leave to be with her, or why won’t he leave me to be with her?

[Anonymous]

My b/f and I have been together for 15 years now, while we are not married or live together we do have a 13 year old son together, I do have keys to the house and do everything married couple do even paying bills we just don’t live under the same roof mostly due to him owning his home and I owning mine and neither willing to give up there homes. Well that’s what I thought I have now found out that his been cheating on me for 12 years now She has always known about me and encouraged my B/F to stay committed to me even after I walked in on them in bed together which is when the affair was exposed.
What would motivate a woman to be a mistress yet be happy to never be anything more and encourages him to stay in a relationship with their significant other?
Why wouldn’t he leave if he claim to love both his mistress and significant other?
Is it better to stay friends or walk away completely after finding out what he had done?

[OlderAndWiser]

1. Whatever happens in your relationship, he is still your son's father. You can't just walk away and never see him again.

2. For some people, the thrill comes from the fact that it is cheating. Legitimize their relationship and it is no longer cheating, no longer thrilling, and he may start cheating on her.

3. Maybe she is married or has a long term boyfriend.

[boggboss]

Why wpuld he if he dont mind the situation why wpuld u need him to make the choice clearly u ain't happy yet you need to ask what u should do

[Berethor]

He claim to love both his mistress and significant other, polyamory? also the child bond.

[Anonymous]

Does it matter? Just dump that clown and move on.