Finally about to fulfil your Fetch name promise? (Still waiting to see you at parkrun btw....
The only knowledge I have of having two dogs was my BiL, who got a second male Golden retriever pup when the first was about 8. Harvey had been neutered and was used to sharing walks and being looked after on holidays with friends with another dog, so he took Frankie's arrival in his stride. Frankie seemed to learn a lot of basics - barking to be let out for a pee, eg, from him. When Frankie got a bit too much Harvey would tell the puppy off but nothing to be alarmed about, just a quick bit of swearing.
Frankie was neutered too when he was about 18 months old, by which time the two dogs had got quite used to each other and rubbed along ok. I wouldn't say they were bosom pals, but they didn't show any signs of jealousy either.