Why Blake Lively and Ryan Reynolds fight over their baby

Blake Lively and Ryan Reynolds have apparently been fighting a lot lately.

And the actress told Jimmy Fallon Tuesday night their bitter feud is all over their 4-month-old daughter's first word.

"We're total rivals, by the way. So like, you hear [Ryan] like, 'Dada, Dada' all the time. And then I walk in and he's like, 'Mama!' And I'm like, 'How dare you do that?' But all day, the word 'Dada' is banned in our house," said Blake Lively on the "Tonight Show."

And why is baby James forbidden from saying "Dada" first, you ask? It's actually quite simple.

"She has to say 'Mama' first! I do everything. He does nothing," said Blake.

Beautiful celebrities - they fight over their spawn's first words, just like us.

We're secretly hoping James's first word is anything but "Mama" or "Dada" now. You know, just to up the drama ante a little. But that's just us.

But don't worry, Blake and Ryan aren't fighting about much else when it comes to their bundle of joy.

In fact, the proud mom admitted on "Live with Kelly and Michael" Tuesday she and Ryan are even sharing diaper changing duty.

"And how is he? Does he change the diapers?"

"Now he just smells like poop."

"I think it's pretty, uh, it's pretty equal. Yeah, we're pretty good, yeah."

And their helpful parenting style has even allowed Blake to juggle acting as well as being a new mom. You can catch her in her latest flick, "The Age of Adaline," when it hits theaters April 24.