Step son and son dont get along 😩

I’ve been with my partner for 3 years, his son has been coming to mine for 2 and a half years now at weekends for sleepovers ☺️ he is 5 years old now and so is my son, one problem is though, they both don’t get along at all!!!

Since the very beginning they argue 24/7, they can’t agree on anything, I have to separate them most of the time as they even lift their hands to each other, I’ve tried talking to them, playing with them to encourage nice play but nothing is changing and it’s been nearly 3 years now, if anything it’s getting worse 😩

I feel their personalities clash a lot, my son is very loud and hyperactive and wants to play with the kids all the time. My step son is quieter, likes his own space and prefers to sit with adults.

I’m at my wits end with this and so is my partner, we’ve got a baby on the way and I can’t handle the stress of them being together the now, it’s becoming too much. They are perfectly fine when alone and when playing with other children it’s just with each other they are like this😩

I need advice, baby is due in November and I’m worried I’m not going to cope when I have all 3 at same time, just with how much they fight😩