How do i tell my family im dating my ex?

[Vanessa]

Best thing I can say is to just sit her down and have a heart to heart. Ask her not to get upset, and you have something you feel you need to be honest about and tell her.
Considering you broke up with your last boyfriend and went back to your ex can say something about your ex. Explain that to her. You're back with him for a reason. Tell her how happy he makes you. If you feel that being with your last boyfriend made you realize how much you cared about your ex, tell her that, too.

Parents tend to get upset sometimes when they don't want to hear something, but in the end, they do appreciate honesty.
Just be open about how you feel.