Other Vampires you control get +1/+1.

When Edgar, Charmed Groom dies, return it to the battlefield transformed under its owner's control.

At the beginning of your upkeep, create a 1/1 white and black Vampire creature token with lifelink and put a bloodline counter on Edgar Markov's Coffin. Then if there are three or more bloodline counters on it, remove those counters and transform it.