Help for Two Dogs Not Getting Along

Can anyone offer some advice for my cousin, please?

As per my photo post the other day, she got a new dog; Jackson. He is 10 months old and entire.
Alfie is also entire, about 6 years old. Alfie doesn't actually live in my cousins house, but is there for a week or two every couple of months

Probably the wrong time to bring Jackson in, but whats done is done I suppose and she's rather not get rid of him.

Alfie gets on absolutely wonderfully with my youngsters (included Rory, who is not neutered; 8 months and a smaller breed so ignoring size I wouldnt have thought he'd be too different from Jackson).
He's been on walks with Jackson and mostly ignores him - he's never been much for playing with other dogs.
In my cousins garden the two are mostly fine, until Jackson wants to play which is when Alfie will snarl and growl. If Jackson doesnt move away, things escalate a little and they scuffle.
Inside the house, Alfie snarls almost constantly.

Having seen full on dog fights, blood and all, I'm thinking Alfie is not trying to hurt Jackson at all and is just trying to put the rowdy pup in his place.

He he getting told off for growling, rather than the pup for pestering, which I've said something about.

Alfie is at my house right now and he goes on a walk with Jackson every day, but I'm thinking thats probably not the best course of action and he should be there in the house where the issues are!

Jackson is due to be neutered next month, but obviously thats not going to be a quick fix, if it does anything at all.

Should the two be allowed to duke it out as long as someone steps in before (if?) it gets nasty?
Baby gates in the house to keep them separate but still in each others presence?
Just looking for advice to pass along

The duking it out would have been ok if the youngster got the message but seems he hasn't so older One needs the support . Time outs crates. stairgates etc good younger One needs an outlet ofhis own perhaps some toy based training. older One needs praising and rewarding for any good interactions that show tolerant.and accepting behaviour and. Soft body language whilst not Hal.g allowed to being put in the. situation where he has to act, ie, remove the pressure . sorry that's the best I can manage on a smartphone keypad others would probably flesh. that out ....ps - clicker for youngster. = mental. tiredness

Oh, wonder. I've got this same problem! A rowdy Nigredo, at 8 months pestering an older Jade and ugly snarling and stuff escalating from not interfering.

I don't have any real advice because I am struggling to control my own problem. I'm going to try the gates, several people have recommended that.

Normally I let the dogs duke it out and simply find their places among each other but I've learned that there are cases where this isn't effective and/or can be dangerous.

Also, I don't reprimand Jade for growling at Nigredo, but rather I tell Nigredo off for bothering Jade. All I have to do is clap or call his name and that gets him off, if he persists... I'll raise my voice, gets the job done.

Two entire males = potential big problem. Good luck! I'll be following this thread (why I commented) hoping it will help me, too!!