Former All Black and broadcaster Murray Mexted is in for some sleepless nights after last month becoming a father again at the age of 55.

The outspoken rugby commentator and his South African girlfriend Mariska Meyer - little more than half his age - welcomed a baby into the world a few weeks ago, but are saying little about their new arrival.

Mexted, who already has two children, Hilton, 15, and Jasmine, 10, with former wife Lorraine Downes, would not discuss his new bundle of joy, who was born at Wellington Hospital.

It's believed that Mexted, 55, and Meyer, who live in Wellington, have been together for about four years. Meyer works in administration at the International Rugby Academy, of which Mexted is managing director.

The former All Black is understood to have kept the birth so secret that many of his Sky Sport colleagues did not learn of the baby until recently.

Mexted and Downes separated in 1999 after 13 years of marriage.

In February Downes wed former cricket international Martin Crowe.

While Mexted might have thought his nappy-changing days were behind him, he's in good company as an older dad. Wellington property magnate Sir Robert Jones, 69, has children whose ages range from 4 to 40, and 75-year-old Auckland designer and cartoonist Peter Bromhead's children are separated by a 50-year gap.

Bromhead already had four children from two previous marriages when his son, Oscar, was born three years ago. His eldest "child", Esme, is now 53.

In his second marriage, Bromhead become dad to Tim, 28, Kitty, 25, and Thomas, 22.

"As an older father I'm putting in far more time with[Oscar] than my previous, grown-up family," said Bromhead, whose wife Caroline is 34.

Internationally famous older fathers include David Letterman, 62, whose only son Harry is 5.

Rupert Murdoch, 78, has six children aged between 50 and 5 years.

And Rod Stewart, 64, has six children between 29 and 3, as well as an adopted-out 44-year-old daughter he fathered at age 19.