Emily Ratajkowski, 31, and Sebastian Bear-McClard, 41, plan on divorcing because . . . stop me if you’ve heard this before, he’s cheating on Ratajkowski. Page Six’s source, who appears close to Ratajkowski, calls Bear-McClard “gross.” “Yeah, he cheated . . . He’s a serial cheater. It’s gross. He’s a dog.” Although the two haven’t filed for divorce yet, it’s been in the works. One anonymous submission to DeuxMoi said a “gorgeous model, actress and clothing designer showed up to at Michael Rubin’s party last weekend ALONE.” This was Fanatics CEO Rubin’s July 4th party . . .