Mel Gibson welcomes his ninth child

Rosalind Ross, Mel Gibson
Rosalind Ross and Mel Gibson at the 74th Golden Globe Awards on Jan. 8, 2017. (Jordan Strauss / Associated Press)

Stop us if you’ve seen this one before: Mel Gibson has a new son. He also has a couple of new Oscar nominations for “Hacksaw Ridge.”

Gibson and girlfriend Rosalind Ross welcomed a baby boy on Friday, the actor’s rep confirmed to the Los Angeles Times. Lars Gerard Gibson weighed in at 5 pounds, 5 ounces. He’s the “Mad Max” actor’s seventh son, and his first child with Ross.

Gibson, 61, and Ross, 26 — she’s a writer and champion equestrian…