Farrah Brittany just pulled off a two-for-one reveal ... announcing she's having a baby boy while seemingly confirming Zach Goldsmith is the father.

The "Buying Beverly Hills" star shared a gender reveal video Sunday -- captioned, "We're having a...." -- and Zach was right there beside her for the big moment.

Farrah's sister Sophia documented the buildup ... grabbing pink and blue balloons, an Hermès gift and even matching cat collars before the family learned the results.

Then came the reveal -- it's a boy!!!

And, while everyone celebrated, Farrah and Zach turned toward each other and embraced ... a pretty telling moment considering she's kept the identity of her baby's father under wraps since announcing her pregnancy last month.

Zach wasn't exactly a random face in the room ... he and Farrah worked together at The Agency and appeared alongside each other on Netflix's "Buying Beverly Hills."

As TMZ previously reported ... Farrah announced in July she was expecting her first child, but didn't publicly identify the dad at the time.

There'd already been plenty of speculation about Zach ... and Sunday's video appears to finally let the cat out of the bag.

Baby boy ... and baby daddy reveal!!!