At one point, Gilbert, who runs the Olde Salem Magic Shoppe out of the sisters' former home, shares that he was a trick-or-treater on Halloween night in 1993. Apparently, he saw the witches take flight on their broomsticks that fateful evening, leading him to become just as obsessed with them as the rest of us. He also reveals that he had his candy stolen by Jay and Ernie, the bullies from the first film.
Also, Gilbert has a black cat named Cobweb who lives with him at the magic shop, and while a connection to Thackery Binx is never made explicit, it's also never clearly said that he isn't a human soul trapped in an animal's body — so there's definitely room to explore that.