I say set them up to succeed. If they fight over toys; remove that stimulus from the room. The toys are YOURS - not the new puppys. YOU will decide when and how they are played with. He needs to understand he is NOT the alpha in this house.
When we first brought Lucy home; Ringo guarded all the toys. We took them all up and when things were going well, we would introduce one or two into the room.
Now, of course, the toys are laying all over the place. But when you have an aggressive, dominant male, or problems in the relationship, take away the things that cause problems. Later, you can lighten up.
Do everything to get them started off on a happier note before your oldest refuses to have anything to do with the pup.
Start working on basic commands with your puppy; sit, down, etc. Gently get him used to obeying your commands. Ask him to sit before you feed him; lie down before a treat . . . little things like that can reinforce your position as leader. Sounds like he wants to be the leader right now.
__________________  Mommy to Lucy, Ringo, and Matthew |