Baldwin baby battle.

Alec Baldwin couldn’t believe older brother William “Billy” Baldwin had so many kids — but the “30 Rock” actor wound up with eight of his own.

The “No Address” star, 61, recently got candid about how Alec, 66, teased him after he and wife Chynna Phillips became pregnant with their third child.

The couple tied the knot in 1995 and have daughters Brooke, 20, and Jameson, 24, and son Vance, 24.

“I remember when he made fun of me when Chynna and I were pregnant with our third child,” Billy exclusively told The Post while promoting his new film “No Address” on Monday. “He said, ‘What are you, dad?’ Because my mother and father had six kids.”

Along with Billy and Alec, their parents Carol and Alexander, had Steve, 58, Daniel, 64, Elizabeth, 69, and Jane, 60.

But the “Lead With Your Heart” actor gave it right back to the “Drunk Parents” alum, who was previously married to Kim Basinger from 1993 to 2002 and with whom he has daughter Ireland, 29.

“And then he got married again and he had child three, four, five, six,” Billy recalled, “and I said, ‘What are you Anthony Quinn?'”

“And that’s a joke because there is an actor, Anthony Quinn, who when he was [82] had a child,” he added. “Tony Randall had a child at like 75.”

These days, Alec has a full house after marrying wife Hilaria Baldwin in 2012. The couple welcomed kids Carmen, 11, Rafael, 9, Leonardo, 8, Romeo, 6, Eduardo and Marilu, 4, and Ilaria, 2.

And now Alec and Hilaria are set to debut their new TLC reality show “TheBaldwins” on Sunday.

But regardless of having one or eight, Billy knows things change drastically when you become a parent.

“My life was never the same,” he said. “I never really slept the same. You don’t really sleep the same. Your kids go out on a sleepover, or they are 14 and go out to a party and you’re sort of sitting in bed and your eyes are closed and you’re asleep but it ain’t the old sleep!”

These days, with his kids all grown-up, the actor has time to spend working on projects close to his heart, including the new Robert Craig movie “No Address.”

The film, which also stars singer Ashanti, Xander Berkeley and Ty Pennington, explores the homelessness crisis in Los Angeles and across America.

“They follow the path of five or six different stories. A veteran who becomes homeless, a young woman in foster care who ages out of foster care, someone experiencing a mental health crisis in their life,” Billy said.

“My character is really the proof that you’re one job — being fired from one job, you’re one whooping medical bill, you’re one gambling or addiction crisis or natural disaster away from living in your car,” Billy added. “There are a lot of people right now in Altadena and the Pacific Palisades that have insurance and there are many that don’t.”

In order to get the movie just right, a lot of pre-filming work went into it.

“We did a lot of research and preparation, they were in 20 cities, 18 states,” Billy told the Post. “Meeting with federal state local officials, nonprofits [and] faith-based organizations trying to get everything honest and accurate on the screen.”

The advocate took a moment to reflect on how the homelessness crisis has changed over the years, noting that there is hope for things to get better.

“It was bad but then COVID made it much worse,” Billy said. “Fentanyl’s made it much worse. Political instability causing refugees and migration have contributed to it. It’s a complicated issue but we have the resources to drastically, vastly improve the numbers, if we have the political will, we will do it.”