AITA for telling my ex-wife’s new husband that I’m still financially supporting our kids, and he needs to back off?

I (38M) have two kids with my ex-wife (35F), Ella. We’ve been divorced for 4 years, and we have joint custody of our kids (8F and 6M). I’ve always made sure to pay child support on time and even give extra when needed, like for school supplies or extracurricular activities.

Recently, Ella married a man, Greg (40M), and ever since, he’s been trying to insert himself into the financial side of things. He’s been pressuring me to pay more money for the kids, saying it’s “unfair” that I don’t contribute more to their lifestyle and that I should pay for things like their vacations, the kids’ school fees, and gym memberships.

I’ve tried to politely set boundaries, but he keeps pushing, saying I’m not being a good father. I lost my temper and told him that he’s not their father, and if he’s trying to tell me how to support my kids, he can back off and take responsibility for his own kids.

Ella is now furious with me, saying I’m being rude to her new husband and causing unnecessary tension. Her family is also upset.

AITA for standing my ground, or should I have just let Greg take over the financial side of things?