Aw, Kid . . .

So that’s how it works:

A class-action lawsuit against top real-estate broker Brown Harris Stevens alleges the firm discriminated against families that were trying to rent apartments in Brooklyn — because they had kids.

The suit, filed Thursday, is the first class action against a real-estate agency for “assisting and enabling landlords to carry out the discrimination,” said Diane Houk of the Fair Housing Justice Center.

One agent allegedly told Jamie Katz and his wife, Lisa Nocera, “I’ll show you everything available that I think is suitable for kids.”

They first went to Brown Harris Stevens two years ago when they saw a listing for a converted carriage house in Brooklyn Heights.

Nocera was nine months pregnant, and they wanted to leave their tiny Manhattan apartment. But the broker didn’t show it to them, saying “the owners would not rent to people with children because there was an outdoor space,” according to the lawsuit.

The couple remained in Manhattan, but when they looked again last June, with their baby, Bruno, they liked a $2,300-a-month apartment in Park Slope. After filling out an application, a Brown Harris Stevens broker allegedly said the owners wouldn’t rent to anyone with a child because of lead paint.

“I felt bad,” Katz said. “I felt they were preying on our fears as new parents about lead paint.”