Alex Rodriguez is one proud papa!

The former MLB star took to Instagram on Friday to wish his youngest daughter, Ella, a happy birthday, with an adorably sweet message and snapshot.

WATCH: Jennifer Lopez Holds Hands With Alex Rodriguez on Dinner Date

"Nine years ago today my baby girl was born and every single day since then has been filled with love and joy," he captioned a stunning black-and-white shot of the two cuddled up together. "My lil wild child... daddy adores you."

"Hope you have the happiest birthday ever!!" he added. "I love you Ella Bella."

Earlier this month, the athlete also shared a photo of his "fun day in the Bronx" with Ella and her older sister, 12-year-old Natasha.

"#Daddysgirls," his hashtag read.

Rodriguez, 41, started dating Jennifer Lopez, 47, last month, and things between the two have been heating up fast. In addition to trips to New York City, Miami, the Bahamas and the Dominican Republic, the lovebirds recently introduced their children to each other.

WATCH: Jennifer Lopez Shares Lookalike Pic of Daughter Emme and Alex Rodriguez's Daughter Natasha

Lopez, who is the mother to 9-year-old twins Emme and Maximilian, even shared a photo from their get together to Instagram.

Hear more (and see the pic!) in the video below.