The fashion designer’s son Alex and his fiancée Ali Kay welcomed their son into the world on Monday. Leon was born in Los Angeles and is named after Diane’s father.
“All good! Love is life,” she said in a statement to New York Post.
The 65-year-old designer has two kids and Leon is her fourth grandchild.
Alex was apparently away traveling when Ali went into labor, so immediately caught a flight back to America from the French Riviera.
In March, Diane gushed about how much she was looking forward to the new arrival while giving a talk to students in New York City.
“I’m going to spend a fortune on that one,” she said. “I haven’t bought anything yet; I’m very superstitious.”
Diane has spoken about her family life at length. She credits her mother with giving her a desire to succeed and although she loved her childhood she’s happy to be getting older.
“I really, really do not envy the young, and I don’t understand Peter Pan syndrome, when people say they don’t want to grow up. I always thought the condition of childhood was a sad, sad thing,” she said.