My ds age 5 has always been hard work and jealous in a (imo) normal way of his younger sister (almost 3). We also have another dd age 7.
But lately I feel the nastiness towards her has become quite extreme. He also fights with dd1 who is older but she can handle him, iyswim. As soon as he comes home from school it starts. I give them a snack then they go off to "play" and all I can hear is "You're so stupid", "I'm never going to let you play with me" etc etc, usually followed at some point by a physical assault and dd running to me crying. I try to let minor stuff go and leave them to sort it out but I've been watching without them seeing me and dd hasn't been doing anything to provoke him. I give him a telling off and put him in time out if he makes dd cry.
Yesterday he said out of the blue in the car that he wished dd2 was dead. I know he doesn't mean it but it shows a lot of resentment imo. I've asked him why he's saying mean thigs to dd but he just shrugs and laughs.
I can't think of any reason why it should have suddenly got worse. Is this still normal sibling rivalry or should I be worried? I'm an only child so this is all new to me.
Thanks in advance.