Caitlyn Jenner has become a grandmother for the sixth time.

Caitlyn Jenner and William Behr (c) Instagram

Caitlyn Jenner and William Behr (c) Instagram

The 69-year-old star shared an adorable photo of herself with little William Behr - the son of Caitlyn's oldest son Burt and his partner Valerie Pitalo - on her Instagram account on Sunday (17.02.19), a week after the tot was born on February 9.

Caitlyn captioned the post: "Welcome to the world William Behr Jenner. Congratulations @burtonjenner and @valeriepitalo !! Love you guys (sic)"

It has been suggested the baby took his first name in honour of Caitlyn, who was born William Bruce Jenner.

Burt announced the arrival of his second son by sharing a cute video of his eldest child, two-year-old Bodhi, cuddling his baby brother and declaring him to be "nice".

As well as Bodhi and William, Caitlyn is also grandmother to her daughter Kylie Jenner and Travis Scott's 12-month-old daughter Stormi, her elder daughter Cassandra and husband Michael Marino's three kids, Francesca, 10, Isabella, seven, and Luke, two,

and son Brandon Jenner and his ex-wife's three-year-old daughter Eva.

Burt, 40, has previously revealed he was "excited" when Caitlyn came out as transgender and insisted he had always supported her and the wider LGBT community.

He previously said: "I'm very excited [about Caitlyn's gender affirmation]. Part of me was screaming to say, 'Hey, I've known for 25 years and I've always been supportive! I always will be.'

"Before I was allowed to tell anybody, or before my dad even knew that I knew, I went and marched on behalf of Prop 8 through the streets of Los Angeles. I've always tried to be an outspoken supporter of the LGBT community."