Eight years ago, after the birth of our twin children, my former partner and I decided to go our separate ways. We had been dating for just over a year when she became pregnant, and although we tried to stay together for the children, it wasn't meant to be. She soon found someone new and yearned to pursue that relationship. Our split, while peaceful, marked the beginning of a challenging co-parenting arrangement.

Initially, co-parenting went smoothly. However, when my ex remarried to a man who was also a single father, the dynamics began to shift. He had a daughter the same age as our twins and insisted that I should treat her as part of my family, expecting me to include her in gift-giving and outings with my own children. This demand complicated our interactions and subsequently led us to adopt a parallel parenting approach to avoid conflicts.

We share custody equally, and neither of us pays child support since we both have the children for equal amounts of time. I maintain a close bond with my twins and, during my allotted time, I focus on them without including the other children from their mother's household. Over time, their family has expanded to include a stepsister, a stepcousin who moved in three years ago, and a younger half-sister, adding more complexity to the family structure. Another child is possibly on the way.

The current disagreement stems from an upcoming class trip in November. The school our children attend is rather small, leading to shared classes between them and their stepsiblings. This trip, to an interactive museum, is quite costly, but I can afford it and my twins are excited to go. I decided to pay for them, but this decision didn't sit well with my ex and her husband. They felt that I should also pay for their stepsiblings' tickets or else let none of the children go. They argued this would avoid any feelings of exclusion and maintain family unity. I disagreed, emphasizing that it was my right and decision during my parenting time. This led to accusations from my ex’s husband that I was undermining their family dynamics and fostering resentment among the kids.

Do you support my decision? What do you think? Am I wrong?

Should I have paid for all kids' class trips?