Ethel and Bobby Kennedy playing with two of their children. (Paul Schutzer/Time & Life Pictures via Getty Images)

Rory Kennedy and her 10 siblings never thought it was fair when people would say, “You’re Bobby Kennedy’s kid.” Certainly, they loved and were proud of their father, but it was mostly their mother, Ethel, who raised and nurtured them.

So the documentary filmmaker, born six months after her father was killed in 1968, turned the spotlight on her mother. “Ethel” looks at a very public life through a very private lens — candid interviews with her brothers and sisters, family and historical photos, home movies and a one-on-one interview with her mother, who has always pulled a curtain around her family life.

“I anticipated that my mother would not want to do it, because she’s never really told her life story,” Rory told us at a screening Thursday at the Motion Picture Association of America. “The truth is, I called and asked her, and she said yes immediately.”

“It’s very hard to say no to Rory,” her mother said.

Rory and Ethel Kennedy at the MPAA screening Thursday. (Photo by Ralph Alswang )

What emerges is a surprisingly compelling portrait of a lively, spirited woman with a fierce sense of loyalty, deep religious beliefs, a boundless sense of fun and little fear of authority. (Ethel was arrested for stealing a neighbor’s mistreated horses; she won the case.) The family tragedies are there but — following Ethel’s example — not lingered on.

That’s the woman HBO executive Sheila Nevins met 12 years ago in Cuba, when she came up with the idea for the documentary, which debuts on the cable channel later this month. Nevins thought it would be a mother/daughter story; instead, it has touched a political nerve. At the Sundance movie festival, there were lines around the block.

Part of it is the Kennedy magic, but part is nostalgia for a time when people weren’t cynical about politics and politicians. “I thought it was past history; it turned out to be present history,” Nevins said. “I thought it was a small film with a big heart about a time that was. I didn’t know it was a bigger film about a time that isn’t and that it would attract young people.”

Ethel’s take? “I think it’s a tribute to Rory’s talent. She’s amazing. She can make a lot of very little, and she did.”

Spoken like a proud mom. “It’s true, I am,” she said with a broad smile.

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