The former New York Yankees baseball player turned 44 on Saturday, July 27, and the following night was commenting on his old team's' game against rivals the Boston Red Sox for U.S. network ESPN's Sunday Night Baseball.
But during the broadcast, the "Medicine" hitmaker surprised her fiance, along with with his daughters, Natasha, 14, and 11-year-old Ella, to present the former sportsman with a sweet birthday cake.
The move comes after the "Jenny From the Block" star paused her show at the American Airlines Arena in Miami, Florida, to bring her beau out on stage and present him with an epic four-tiered Yankees-themed cake.
She also honoured Alex with a sweet Instagram post, writing: "Celebrating you today and everyday my love...You are one of a kind, my hurricane and my calm in the middle of the storm...thank you for being such a beautiful light in my life."
She conclude her post: "Wishing you the most beautiful birthday ever!!! HAPPY BIRTHDAY 13 (his old baseball number)!!!".
Jennifer has been touring the U.S. with her "It's My Party" tour since June, but the star took a night off on Wednesday to celebrate her 50th birthday.