Three years ago, Cristan Crocker Reilly and Andrea Blaugrund Nevins set off on a mission to produce a feature docu about fatherhood as seen through an unusual prism: Punk rockers.

The end result, “The Other F Word,” will have its world premiere Saturday as an official selection of the SXSW film fest in Austin, Texas. The stories they wound up telling in the pic turned out to be very different than what they expected.

“We went in thinking, ‘Oh this is going to be so funny.’ The punk rock dad — it’s so antithetical. The guy who is all anti-authoritarian now has to be the absolute authority,” Nevins says. “And it wasn’t that at all. To watch these men come to terms (with fatherhood) and speak about it was shockingly moving to us.”

Nevins, who directed the pic, and Reilly, who produced, found their throughline for the pic early on in the fact that most of the musicians featured in “F Word” had difficult childhoods and no strong father figures to lean on when they were kids.

“They were all drawn to punk rock for a reason,” Reilly says.

Reilly was inspired to pursue a docu after she read the book “Punk Rock Dad: No Rules, Just Real Life” penned by Pennywise lead singer Jim Lindberg, a friend from her high school days. She brought the book to Nevins, a TV news and docu producer who earned an Oscar nom for the 1997 short “Still Kicking: The Fabulous Palm Spring Follies.”

Reilly and Nevins have been friends for years, having met through their husbands — Fox Broadcasting’s Kevin Reilly and Showtime’s David Nevins. Nevins had considered herself “retired” from producing while she focused on raising three children. But when Reilly, also a mother of three, asked her to think about helming a docu based on Lindberg’s book, Nevins called her 48 hours later and said “I’m in.”

Docu maven Morgan Spurlock had the same reaction when the two pitched him the project over breakfast. “By the time we were done with coffee, he was our executive producer,” Nevins says.

The initial plan was to focus on Lindberg and his struggle to balance the demands of parenthood while on a grueling national tour. But Lindberg kept pointing the duo to other musician friends who are fathers, so the pic expanded to include such notables as Flea, Mark Hoppus of Blink-182, Art Alexakis of Everclear, Brett Gurewitz of Bad Religion, Tim McIlrath of Rise Against, Fat Mike of NOFX and Ron Reyes, the reclusive former frontman of Black Flag.

“F Word” was produced in the grand do-it-yourself tradition of punk rock. Reilly and Nevins financed the project on their own, to ensure they retained creative control. (WME is shopping it for distribution.) The crew on shoots that ranged as far as New York, Chicago and Vancouver consisted of Nevins, Reilly and d.p. Geoffrey Franklin, who also edited the pic. The grassroots approach encouraged the participants to give “F Word” a break on costly elements like music rights.

“Our biggest accomplishment was satisfying the punk community, having them watch it and say that we got it right,” Reilly says. Adds Nevins: “We feel like we’ve made a punk rock documentary that you’ve never seen before.”