Ronnie Wood is set to become a grandfather for the eighth time.
Leah told the new UK issue of HELLO! magazine: ''We took dad out to lunch and broke the news that he's going to be a grandpa again.''
The 35-year-old blonde - who lives with mother Jo in north London - already has a four-year-old daughter, Maggie.
Her second child with Jack is due on their daughter's fifth birthday in May.
Leah revealed: ''Dad is really good with Maggie. We don't see him often but when we do, he'll pick Maggie up and give her kisses and play with her.
''She will see him on TV sometimes and say, 'Ah, it's Grandpa.'
''But she's obsessed with Keith Richards. He'll go up to her and he'll kiss her hand and she's like, 'Oooh!'
Guitarist Ronnie and ex-wife Jo divorced in 2009 after he left her for young waitress Ekaterina Ivanova. He is now married to theatre producer Sally Humphreys, while Jo remains single.
The former couple, who remain close, are also parents to Tyrone, 30, Jo's son Jamie, 39, and Ronnie's son Jesse, 37.