Jade Jagger has given birth to a baby boy.

The 42-year-old model - whose 21-year-old daughter Assisi Jackson gave birth to a baby girl last month - has welcomed her third child into the world, according to HELLO! magazine.

The British jewellery designer, who also has a 17-year-old daughter, Amba Jackson, with ex-boyfriend Piers Jackson, revealed in February that she and her art designer husband, Adrian Fillary, were expecting their first child together.

She proudly showed off her growing baby bump in a photograph on Instagram, with the caption: ''Happy to announce this granny is going to become a mummy I'm 6 months pregnant xx double whammy this year.''

The couple tied the knot in a lavish ceremony at the luxurious Aynhoe Park hotel in the Cotswolds, England in July 2012.

The arrival of Assisi's baby girl last month made Jade's father, Sir Mick Jagger, a great-grandfather for the first time, and Assisi previously insisted he was thrilled about her pregnancy.

She said: ''He said, 'Well done,' and I said, 'I didn't have to try too hard.' ''

But she added: ''I imagine it's nice to be a great-granddad - although I'm not sure he likes the idea of getting old, or being called one.''

Jade's new son is The Rolling Stones rocker's fifth grandchild.