Saoirse Kennedy Hill wasn’t a known party girl, a source close to the family said Friday.

The 22-year-old granddaughter of Robert F. Kennedy was found in cardiac arrest Thursday around 2:30 p.m. at the sprawling Kennedy estate in Hyannis Port, Massachusetts. She was pronounced dead at the hospital.

An emergency operator had told responding cops that there had been a reported “overdose” at the compound.

The family source insisted that very little drinking and partying has recently taken place at the 6-acre waterfront compound.

And “there’s never been any sign to the family that Saoirse was drinking or taking drugs. She wasn’t a partier or anything,” the source told Page Six.

The source said much of the adult family — rocked by decades of tragic events that have become known as the “Kennedy curse” — are sober.

The same source, however, noted Saoirse’s “very difficult upbringing,” as well as her issues with depression and the sexual assault she experienced as a teen.

She is the only daughter of Courtney Kennedy Hill and Paul Hill, an Irishman who was wrongfully convicted in a pair of Irish Republican Army bombings in 1974. He and Courtney married in 1993 and split in 2006 after living for years in Ireland.

“Basically, Saoirse had a very troubled, unstable childhood and life until the time that Courtney and Paul separated, and then Courtney and Saoirse moved back to the Cape, where they’ve been living full-time for about the past 10 years,” the source said. “This girl is very sweet and a very shy girl who has struggled a lot with depression since her early teens.”

Additional reporting by Lia Eustachewich