Matthew McConaughey and Camila Alves may have to start acting as referees soon. Their kids Levi, 2½, and Vida, 13 months, are gearing up for a pretty intense sibling rivalry, according to Pops!

“[Levi] dotes on her, but [Vida is] getting big enough where it’s a competition now and he’s only got a few more months of being bigger than her,” McConaughey, 41, said on the Oscars red carpet Sunday.

“She’s gonna overtake him I think and really start whooping his butt soon!” he laughed.

“I have to agree with you,” Alves, 28, admitted with a smile.

At least McConaughey and son Levi can get in some special father-son time before little sis Vida is old enough to interfere. It’s no surprise that the surf-loving daddy would try to introduce his son to the ocean.

“He’s still a little spooked by the water, mind you that Pacific’s a little colder than that Atlantic,” the actor reported. “He got in the Atlantic quicker than he got in the Pacific–when we went to Brazil. But, I think his sister’s probably going to be a water bug before he will.”

Alves was also delighted to describe her daughter Vida as “a daddy’s girl”, a fact McConaughey does not mind at all. “It’s starting to happen,” the actor said. “It’s nice when they notice the deep voice from across the house and they know it’s papa, they know it’s dad.”