My ex left me for his AP when our first and only child was 6 months old. He moved her in as soon as the divorce was final, engaged shortly after and then married.
I was livid . I was hurt. I hated this woman being involved in my daughters life since before she even turned one year old. When my daughter was a year old , he tried to take her out of state to visit with OW’s friends WITHOUT TELLING ME. I went apeshit, naturally.
At that point I made sure he knew legally he had to make me away, I have to say know an address and phone number of where my child would be at.
I knew my daughter spent a lot of time with OW’s family as well. I never facilitated it, but I couldn’t stop it. The pain that came with it for me was absolutely immense. I couldn’t stop it. But I didn’t have to make it happen.
More time went on, and it just got easier. My ex was always the one to ask me if he could take her on my time to an event. No one else. And if it is something I know she would really enjoy, I would let him take her. If it was just for him to have my daughter as an accessory at a kids party, then no.
FF to nearly 14 years later. They are still married. My daughter is a part of OW’s family. They treat her well. I am friendly with OW. I am friendly with her family. I make sure every decision I make is in the best interest of my daughter. Even if it hurts me sometimes. She knows she has lots of people who love her. She is happy we all get along and can do things together on some special occasions.
This came with a lot of time and pain and maturity on my part.
You do need to exercise boundaries. They are important to establish early on. If your ex would like to have the kids on your time, she needs to approach you, no the OM’s SIL. I would make that boundary clear. That your custody and times should only be discussed between the 2 of you. No one else.
It’s a process, it’s a learning curve, and it’s hard! But eventually, it won’t be so difficult anymore.
Unless someone was ever in this position with young kids and affair partners, they don’t know what comes with this emotionally.
One day at a time. One decision at a time . I think your heart and head are in the right place. None of this is easy, and I was in my 20’s and I didn’t do such a good job of controlling my emotions in the beginning .