Former Geelong superstar Gary Ablett and wife Jordan are expecting their third child, announced on social media on Sunday.

Ablett revealed the news in a birthday post for his son, four-year-old Levi, who appeared holding an ultrasound image.

“The birthday boy wants to share the gift that we as a family have received,” Ablett wrote.

“Happy Birthday my little man, I'm thankful for everyday I get to spend with you.”

The Ablett's already have two children, Levi and one-year-old Grace.

Jordan shared a similar message alongside a picture of Levi, who lives with a rare and degenerative disease.

“We have another gift on the way," the post said.

“Happy birthday to our big four-year-old! You're so loved.”