How would you navigate a relationship with a woman that has a kid, whose father is now upset that she is happy with you?

[Pegases]

Just to clarify, she didn't cheat on him and end up with me. They had a falling out long before me. Once things got serious between us, her ex caught wind, and is now threatening to take her to court because he is still distraught that she has moved on. And its an odd spot for me to be in, because I've never been in this situation before. Any advice is welcomed.

[OlderAndWiser]

The only sane thing you can do is to ask her how she wants you to handle this.