'Flip or Flop' Star Tarek El Moussa Hooked Up with Couple's Former Nanny

Apparently nannies are just too irresistible, because Tarek El Moussa is the latest to get the bug.

We've learned Tarek hooked up with 23-year-old Alyssa Logan, who was taking care of Tarek and Christina's 2 kids and also performing assistant chores.

It's not scandalous like Ben Affleck, Jude Law or Gavin Rossdale. We've learned Tarek and Alyssa began dating in Sept., 4 months after he and Christina separated.

Sources connected with Tarek and Christina tell us ... when Tarek began having feelings for Alyssa, he was warned NOT to date her while she was still an employee. So he essentially canned her, which cleared the way for a romantic relationship.

The video (above) shows Tarek and Alyssa at a Florida Georgia Line concert back in October. Sadly, it didn't last. They broke up later that month.

As we reported, we're told there's still a chance Tarek and Christina will get back together, but we wouldn't put money on it.