How friendly is too friendly?

So as some of you may know, I adopted an unweaned baby lovebird from craigslist on March 1st(did not buy. I am his 3rd owner). After a slightly extended quarantine and a solid vet check, Pistol met the rest of my flock a couple of days ago.

Sometimes when birds meet there is an adjustment period... Not so much with Pistol. Alex likes him(surprise, Alex doesn't even like Fatty), Fatty adores him.... a lot. How much is too much? Fatty regurgitates for him and follows him around. He has gotten pretty aggressive(while still budgie smiling, little turd) to the point he bites the CRAP outta people when Pistol is around. Pistol is still just as sweet as ever regardless of if Fatty is around. If Pistol is around the corner out of view, Fatty goes back to his normal (still impish, but not biting so hard as to leave marks) self. When Pistol is around, Fatty has no interest in listening to me talk(usually one of his favorite things to do). He will play the flapflap game regardless, and even will play it with Pistol(super cute).

I would like for them to be able to interact. Fatty is hated by Alex and so before meeting Pistol, he had taken up the much concerning obsession with the reflection budgie(no mirrors in cages, but there's always something shiny around when you have the eye of a budgie. He even would flirt with his reflection in one of the insect tanks.). I wouldn't mind if they were BFFs(Best Bird Friends), but I would like it if Pistol stayed tame and if Fatty would ease up with the aggression.

Is this behavior because Pistol is so young and Fatty is in protective mode? Or(my suspicion), does Fatty have romantic intentions with Baby Pistol and this will only get worse unless properly managed?

I've never had two different species birds have such affection for one another before, so really any advice here would be appreciated.

I would imagine your adult birds "parental response" has been triggered. They were hormonal and now there's a chick. I don't think they much care it's not their species, some birds in nature actually lay their own eggs in the nest of others and the other birds raise the chicks as their own! I would definitely keep interactions at this point VERY closely supervised, but I think this may be good for everyone involved- baby gets the comfort of adult birds, adult birds get to feel like they're helping raise a baby bird

Budgies tend to have a very affectionate side to them, hence why Pistol could be getting upset as budgies can be too much.
For example its the same with people, not everyone likes everyone. this is the same with birds... I would personally try and separate them if things start to get worse.
But you never know it could be because Pistol is young and isn't used to the affection and in time may get used to it

Oh Pistol isn't put off by the affection. He seems to like Fatty right back. Fatty is getting aggressive with people when Pistol is around. Hope that clarifies.

Well, whaddya know?

Yeah, I guess I'll throw in with the Kiwi posse... probably a baby-chemistry thing, but I also share the wariness and suggestion for great vigilance, along with a readiness to change the course of action if need be.

I'd like to hear from some parakeet peeps... have they seen similar?'Keets are probably the most domesticated little parrots, and I would imagine they have some special proclivities as far as interacting with new birds, baby birds, etc.

Fatty, you little scamp, what are you up to?

I was thinking exactly the same as Kiwi. Quite like when a baby arrives home everyone suddenly becomes enamored with the baby which appears to have happened here and like you see in some animals Fatty may have decided that Pistol is his little baby and of course tis that time of year which will add to Fatty's mood, do you blame him when you gave him that name!

Oh, those budgies. My Pearl is in love with Ducky, and follows him around and constantly tries to inch closer. Pearl has also tried to land on Ducky’s back, but that hasn’t happened in a few days so I’m hoping the behavior has stopped. My problem has been that Ducky is afraid of Pearl when she flies after him.