I have two sons with my ex husband; Cade (14) and Cael (13). Their father and I divorced 10 years ago, and three years later he remarried. His wife came with a girl (12) and a boy (11) of her own.
Problems started that first Christmas when our boys didn't come to his house loaded with gifts for their stepsiblings (which would have been bought by me obviously). I was told I should have bought gifts for the younger children from their new brothers. That was the beginning of what became a shit show.
To make a long story short, my ex's stepkids get whatever they like pretty much. My ex and his wife do not feel my boys should have things that are kept at my house. They feel what the boys own should be shared with the younger stepsiblings and the stepsiblings want everything.
They are also the kids who still to this day will throw a tantrum if they do not get their way. My boys do not like them and hate their dad's house. There have been incidents where their stuff was broken by the stepsiblings in a tantrum. I might think some of it was exaggerated if I did not witness some incidents with my own eyes.