Am I a terrible person?

My best friend has 2 Boys, 1 & 3 year olds and I have a 1 year old boy. She is the best in the world and we do a lot for each other. My problem is I have got this deep dislike for her eldest child. He does not listen and demands what he wants, of course she gives in all the time. It has gone so bad that I cannot spend time with her when she has the 2 kids. The dad takes the eldest for activities sometimes when the eldest will go and I actually try plan to see her then because I cannot stand the ordeal when she has both. He effects my plans with her also as if we plan a day out I’ve had to take her youngest for hours so she could give the eldest whatever theme park ride he wants etc or if we go to a park he will scream and roar and we all have to leave. He rules the house and if my child gets anything like a balloon or a treat he will kick off to the point it’s such a battle and no1 wins. He does not have any special needs that anyone is aware of. I am fully aware her parenting style is different to mine and that his tantrums are hers to deal with but because of this I really struggle to give him any time. I’ve taken her youngest overnight 3 or 4 times because the dad cannot handle the 2 kids together if she had to somewhere. What do I do? It’s not my place to criticise her parenting nor do I think I have any skills she doesn’t, I just don’t know how to get through this, the child is only 3 and it’s terrible to feel like I don’t even want to be around him.

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