‘Crybaby’ Frank Sinatra would flee and go ‘fetal’ when fighting with Mia Farrow, tried to kill himself when Ava Gardner cheated: actor neighbor

Ol’ Blue Eyes shed a few tears when it came to his wives.

Frank Sinatra would flee his Manhattan brownstone, which is now on the market for $4.45 million, on nights he fought with then-wife Mia Farrow.

“Godfather” actor Gianni Russo, who lives five doors down from where the crooner and the famed actress cohabitated at 249 E. 61st Street, said Sinatra was sure to ring his buzzer.

“Anytime they’d have a fight, he’d come have a drink and spend the night at my place,” Russo, 80, told The Post.

“He’d cry and say, ‘I don’t know what I’m doing.’ This guy was a crybaby, not the image we know of him. He’d get into the fetal position on my couch and go to sleep.”

Russo, who played Carlo Rizzi in “The Godfather,” was 14 and working as an errand boy for Mafia boss Frank Costello when he first met Sinatra at the Copacabana, and they remained friends until his death in 1998.

Russo said he “went through so many romances” with Sinatra, and never understood his friend’s attraction to Farrow.

“I don’t even know why he married her. She’s like a boy, she got no body, she got nothing,” he said.

The “Rosemary’s Baby’’ actress was married to Ol’ Blue Eyes from 1966 to 1968 but continued to be his lover on and off afterward — including when she was involved with director Woody Allen.

Hollywood long speculated that Ronan Farrow, who was born in 1987, was actually Sinatra’s child.

In a 2013 Vanity Fair interview, Mia Farrow was asked point blank about Sinatra’s possible parentage and she replied coyly, “Possibly.”

Russo, who chose Sinatra as his son Luciano’s Godfather, said Ronan’s uncanny resemblance to the “My Way” singer is undeniable.

“That’s gotta be his son. Nobody has eyes like that,” he said.

Russo, a Little Italy native, and Sinatra, who hailed from Hoboken, NJ, shared the same birthday but were 28 years apart.

That didn’t stop them from hitting up nightclubs together, even though Sinatra was hitched.

“When he was with me, he was cheating,” he recalled.

“He was going out with Judy Garland. She had an apartment on 72nd Street, he was dating her. He was going out with Marilyn Monroe.”

Sinatra, who was married four times, couldn’t be single “because he was that insecure,” according to Russo.

The pals were drinking buddies, but when Sinatra — who quaffed Jack Daniels by the bottle — indulged, a darker side would emerge.

“The guy was bipolar. When he’d start drinking, he’d think he was 6 foot 10,” he said.

He could also be depressive.

Russo claims Sinatra tried to kill himself when he found out his then-wife Ava Gardner, to whom he was married from 1951 to 1957, cheated and was leaving him — and went to William Morris talent agent James Woods’ apartment on East 72nd Street to do it.

“Thank God his neighbor was home because there was a gas smell coming from Woods’ apartment,” he said.

“When they went in, Sinatra was half in the oven with the gas on.”

Martin Scorsese is in talks to direct a Sinatra biopic that explores the “violent, sexually charged, hard-drinking Frank.”

Russo doesn’t think Leonardo DiCaprio is a good choice for the title role.

“You gotta have a little bit of balls . . . and he don’t.”