I split with my kids' dad when they were very young. Gave them vague and age-appropriate answers to why we didn't live together as they became old enough to ask. I didn't want to damage their relationship with their dad by saying bad things about his behaviour.
DC are now in their 20s and recently suddenly pushed me on what happened and why you. We were on a walk together, along with their two partners, and I was a bit blindsided by it. DS said he could see I wasn't telling them stuff and I said that I wasn't wanting to talk right then in front of all 4 of them. I am fairly sure one or both of them will pick the conversation back up soon in private.
It's so long ago and something I don't dwell on. But their dad was shit, treating me awfully and chasing after other women. I've never told them this, but they're both very open with me about everything in their own lives including relationships. Is it time to be fully honest and trust that they will forgive their dad? Or should some things stay private?