My ex-husband cheated on me while I was pregnant, and his affair partner had a baby around the same time. We now share 50/50 custody of our son, but we only communicate through a parenting app. I don’t have — nor do I want — a relationship with his daughter from that affair. She’s simply a reminder of a painful time in my life.

Two weeks ago, during his custody week, the school called because no one had picked up our son. I immediately went to get him. When I arrived, I found his daughter waiting too. The school told me I was listed as an approved pickup for her as well — something my ex never asked or informed me about.

I refused to take her. She isn’t my child, and I had no prior relationship or responsibility toward her. I asked the school to remove me from her pickup list. Later, my ex was furious and accused me of being heartless when he found out his daughter stayed at school until 7 p.m.

I told him very clearly: I will always pick up my son, but I am not his backup parent for another child. I don’t feel guilty. It’s unfortunate his daughter waited so long, but her parents are responsible for her — not me. Setting boundaries isn’t cruelty; it’s self-respect.