Well, is probably not the reaction they were expecting.
Arizona couple Jason and Tiffany Mertlich sat their three kids - Gunner and his sisters Harper and Paisley - down last week to tell them some big news: mom and dad are having a baby.
Now after two sisters on the trot little Gunner was hoping they were in line for a little more testosterone around the house - and excitedly tells his folks that he's sure they'll be having a boy.
But as dad reveals that Gunner's instincts are off this time - and a baby girl is on the way - poor Gunner has a meltdown.
"It's another girl," he said. "I hate girls.
"Every time it's girl, girl, girl, girl. … I don't want another girl. It's too much girls."
You'll be glad to know that Gunner got over his initial reaction and is now looking forward to having another sister.
Dad, Jason however, took some flak for his own reaction to Gunner's freakout, when in an effort to calm the kid he empathised, saying "that's how I felt when I found out too".
This didn't go down well online, with many wondering how his daughters would feel about that statement.
"Shame on Dad for saying he had the same reaction!" wrote one.
"Way to raise a male chauvinist!"
However in a subsequent interview Jason said he 'should have bitten his tongue'.