What exactly is it that you're jealous of? Ask yourself that first. Is it them getting romantic attention? Is it because you feel behind? Do you do anything fulfilling in your life? If not try to. Pick up a hobby or make new friends. Also it's okay to hang out with more single people if it helps, sometimes being with too many friends in relationships will only fuel the jealousy and you might realize that you don't actually care as much once you're not around them as much

1