It is quite common for women to go for friends of their exes; but it is not common for a woman's ex and her present partner to get along. Usually these people hate one another, and in case of friends sharing a woman their friendship is often ruined by them wanting the same woman.
I am in an unusual position. I am on good terms with my ex-wife's husband, and I remain good friends with her.
I hope that more people in such situations do the same.
There can be any number of reasons for why a relationship would not work out; but that does not mean that the partners have to become enemies. Remaining friends with an ex is good for the children, and it is also good in and of itself.
Relationship breakdown can be a spiritual test that challenges us to act in a rightful manner. If you love someone, then you should continue to love – or at least like or respect – them even when you are not together any more. Failing to do so invalidates the love that you've had for them and feeds the voices of cynicism, misogyny, misandry and predatory law practices that want people to have no such love and maliciously abuse it wherever it is to be found.
It is frequently said that the best way to lead is by example; and that is what I am doing here. I am showing how exes can get along. I hope that more people take this example and treat their exes right instead of killing them or screwing them over. It is a spiritual test; more importantly it is also a personal test as well as something that contributes to benefit.
The more people do this, the better will be the world.