Michael Phelps, wife Nicole expecting baby No. 3

April 1 (UPI) -- Michael Phelps is going to be a dad of three.

The 33-year-old retired Olympic swimmer announced in an Instagram post Sunday he's expecting another child with wife Nicole Phelps.

Phelps and Nicole are already parents to two sons, 2-year-old Boomer and 13-month-old Beckett. Phelps shared news of Nicole's third pregnancy with a photo of his boys with balloons spelling out "baby."

"#3 on the way! Can't wait to see the journey that this takes us on!!! #luckyman #boyorgirl? #P3," he captioned the post.

Nicole posted the same picture on her own account.

"Oops we did it again," she wrote. "I get to be a mama x3!! #furbabymama x2 #p3 #herewegoagain," she wrote.

Phelps and Nicole also shared the news on Boomer and Beckett's accounts.

"I asked mom for a new baby for Christmas last year and ..... well my wish finally came true!!! I wonder if I'm gonna have little brother or a little sister? #P3," Boomer's post reads.

Phelps and Nicole married in June 2016, shortly before the swimmer announced his retirement for the second time. Phelps is the most-decorated Olympian of all time with a total of 28 medals, 23 of which are gold.