Dog won’t let other dogs play

I’m visiting parents for the month and we have a full house! They have three dogs and I brought my two (all spayed/neutered rescue dogs of various breeds and sizes).
One of their dogs (20lb mix-breed) barks and growls whenever my dogs start to play, well, whenever anyone plays really. He’ll bark and run up to break up, what I assume he thinks, is a fight. My dogs can’t play without this little guy running up and getting between them, occasionally nipping at their heels. My dogs are 50 lb mutts and are mostly just annoyed by his behavior but will stop playing. He’ll even get upset when I’m playing with my dogs; we have to put him in another room and even then he’ll bark and growl if he thinks my dogs are playing too rough with me. My parents say he’s been doing this with their other dogs as well (their 5 lb chihuahuas-mixes).
Any advice on how to train this dog to let my dogs, and really any dog, play? He’s a little fun-police and it’s sad my dogs can’t play.