1. I Pet by Turns
This may be surprising to many dog owners, but you can actually train your dogs to wait their turn to be petted. Once you start the process of just petting your pet, you will find that all dogs come running for that cuddle and love at the same time. what I normally do is address the dogs by their names first and then I do the petting. So I would say venom and them begin to pat and scratch my dogs fur. Then when I am through with that dog I will call the name of my second dog Nica and begin the pet and patting. After continuously following the same method, i realize that the dogs begin to listen for their names to see who first will be petted!
2. Place Them On Both Sides
Well, this will surely work if you only have two dogs, anymore than that and you will probably have to grow a third or fourth hand. So here goes. Place one dog on your left, one on the right and then use both your hands to pet them at the same time. What sometimes happen is that your dominant side may overpower your other side (Lefty or Righty) and as such one dog may just get a little bit more out of that petting. But if this is the case, all you have to do is interchange from time to time.
3. Give The Aggressive Dog a Time Out
If your dog gets to the point where he begins to rattle roughly with the other dog for your attention, he/she may just need to get some time out. But don't make it look like he is being punished. Simply and gently talk to your dog discouraging the behavior while leashing him. Then pet him while on leash and then return to the other dog and pet that dog. If the dog barks and het wiled up while on leash when you try to pet the other dog you have to give him strong "No" commands to teach him to stop.
Dogs just like us humans lobe to be taken care of and loves who takes care of them. They can become jealous for our attention and that jealousy and be a bit overboard sometimes. Train your dog using the steps above so he/she realize that they don't have to be jealous and will get a share of your love.