Former baseball star Alex posted a picture of the On The Floor singer with a huge rock on her finger as the sun set on a beach behind them with the caption “she said yes” on Instagram.
The pair first met at a baseball game in 2005 when they were both married to different people, but started in 2017.
Marking their second anniversary in February, Alex, 43, wrote in a post: "I can’t believe it’s been two years. Only 730 days, which have flown by, but it feels like we have been together forever.
"We are meant to be, and how much you mean to me cannot be put into words."
The pair are famous for gushing over each other on social media.
Jennifer, 49, has previously been married three times, most recently to singer Marc Anthony, whom she has 11-year-old twins Max and Emme with.
Alex was previously married to Cynthia Scurtis with whom he has two children with.
In January the pair put two apartments in New York worth $44.5m up for sale, sparking rumors they were planning to move in together.
Other tell-tale signs came when Jennifer started to cut down on her workload to focus on her relationship with Alex.
An insider told Radar last year: "they absolutely already are acting like each other’s spouses."
“And Jennifer wants to be the traditional partner that Alex needs during this time in their life.”
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