Billionaire Robert Kraft, 80, is engaged to Dana Blumberg, 47

Billionaire businessman and New England Patriots owner Robert Kraft, 80, is set to wed his 47-year-old doctor girlfriend, it has been revealed.

Kraft, who is the CEO of the Kraft Group and worth an estimated $8.3 billion, popped the question to leading New York City ophthalmologist Dana Blumberg with a '10-carat diamond', one source claims.

The couple, who have been dating for three years, had been keeping their news under wraps but Kraft's designer pal Tommy Hilfiger, 70, let it slip at the inaugural amfAR Gala Palm Beach event on Saturday.

Tommy Hilfiger was the honoree and Robert and Dana were both chairs of the event for Tommy,' a source told Page Six.

'[Hilfiger] said his "good friend Bob Kraft got engaged to Dr Dana Blumberg" at the event on stage, speaking to the whole audience.'

Another attendee noted Dr Blumberg was wearing 'a giant rock' at the gala that looked as though it was '10 carats or more', while comparing it to the enormous 'Super Bowl rings' sported by Kraft's Patriots.

The couple's wedding will be the second trip down the aisle for Kraft, who was married to his college sweetheart Myra from 1963 until her death from cancer in 2011.

Kraft had four sons with Myra, all of whom are older than Blumberg: Jonathan, 58, Daniel, 56, Joshua, 54, and David, 50.

One year after his wife passed away, the New England Patriots started dating actress Ricki Noel Lander, now 42; it is thought they parted ways in 2018.

Kraft knew Dr Blumberg as a friend for several years before they started dating. The pair posed for photos together at a 2017 event for the Elton John AIDS Foundation, however they are not thought to have begun dating until 2019.

Dr Blumberg is one of the top ophthalmologists in the US and is based at New York-Presbyterian Hospital-Columbia.