Grandmother to be Jade Jagger has announced that she is six months pregnant.

Jade's 21-year-old daughter Assisi, 21, recently confirmed that she is expecting a child with chef boyfriend Alex and will give birth in April.

Now her jewellery designer mum, 42, has revealed on Twitter that she is expecting a baby a month later, in May.

Showing off her bump, Jade, the daughter of Rolling Stone Sir Mick Jagger and activist Bianca, wrote: "Happy to announce this granny is going to become a mummy. I'm six months pregnant xx double whammy this year."

Jade married DJ and festival promoter Adrian Fillary in 2012, in a bash attended by Jerry Hall, Kate Moss and Jade's parents, Sir Mick and Bianca.

She is also mum to 17-year-old Amba.

Jade's baby will be Sir Mick's fifth grandchild while Assisi's child will be his first great-grandchild.

Assisi previously told Hello! magazine that having a baby young was the norm in her family.

"It runs in the genes. I grew up quite quickly and wouldn't have considered having a child if I was doing what my friends are doing at this stage, messing around," she said.

"I don't drink, I don't smoke and I'm very settled."