Is the pup 8 weeks or 8 months? you said both… He’s jealous! Are you neutering just because of the new dog issues? IMO it won’t help for that, although there are many good reasons to neuter anyway. I’ve had a multi-dog household for years; you have to expect some friction. (Also, older dogs HATE the puppy teeth!) It’s as though your mom brought home a stranger and told you, “Here’s your new BFF!” You won’t automatically get along wonderfully! You should treat the older dog as the #1 dog, even though he’s smaller. For example, pet him first, give him treats first, give him more attention. The younger dog won’t have her feelings hurt, she knows he’s an adult and she’s a baby. Eventually they should get along fine… but don’t rush it. And you may need to protect your older dog from the young one as she grows; she might hurt him accidentally due to the difference in size. My rule for my dogs is, they don’t have to like each other, but they do have to get along. And they do pretty well, most of the time; like people, sometimes they will have a difference of opinion. But they have learned from puppyhood that I don’t tolerate fighting so there is rarely a problem, (Notice I didn’t say ‘never’!:-/) You should google it; there are loads of sites with advice for this. Good luck!