My boys don't physically fight, but they do get jealous sometimes when one is getting attention from one of their humans.
The only suggestions I have are 1) sit on the floor and pet all of them, while trying one in you lap at a time, 2) remove the offenders to another room while you have one on your lap (do this only if you think it is safe to leave the others unattended, out of your sight); 3) work on engaging all 5 at one time with trick training (big challenge
) before you hold one your lap and then give the others commands to wait their turn.
When I see my boys showing jealousy, I redirect their attention by saying, "Do you want to do tricks?" This means they get a kibble for each little trick performed: sit, down, shake hands, and so on. It is much easier with only 2.