Sisters Kate and Anna McGarrigle have an Irish surname, sometimes sing songs in French, and these days, may be better known for their relation to a popular young male singer.

But the McGarrigles, who perform at 7:30 tonight at the Camden Opera House, have no shortage of folk music credibility and remain popular with their audience, even though they tour and record sporadically.

Kate is the mother of Rufus Wainwright, the critically acclaimed singer-songwriter whose father also is a folk luminary, the legendary Loudon Wainwright III.

In a telephone interview from her Montreal home, Kate, 58, betrayed her 1960s Bohemian roots as she chatted away on a host of topics ranging from President Bush – “He talks like he’s got a [computer] chip in his head” – to observing that Christian crusaders wore an early version of denim, the fabric favored by her generation – all in a mesmerizing, late-night-at-the-coffeehouse voice.

“People in the music business have liked us,” she said, as if mildly surprised. “We’re sort of seen as mavericks.”

Almost 30 years after their first record, the sisters have released fewer than 10 titles in all. Royalties from covers of their songs – by Linda Ronstadt, Emmylou Harris, and others – have paid the bills over the years.

Though the McGarrigles began recording in the 1970s, and had their biggest success in that decade with 1977’s “Dancer With Bruised Knees,” a record that still makes many best-of lists, Kate returns to the 1960s to explain her musical beginnings.

At the age of 15, she was encouraged to listen to 1920s Library of Congress folk recordings, from which such artists as Joan Baez drew inspiration. When Kate began watching Hollywood movies, her mentors steered her instead to the arty films coming out of France, Italy and Sweden.

And though her father had some trepidation, he gave his blessings when she hopped into a car to drive from rural Quebec to New York City to see Bob Dylan perform his first concerts in 1963 and 1964.

One mentor who took the McGarrigles under his wing was Montreal native Galt MacDermot, who later composed the musical “Hair.”

Now, McGarrigle is watching her son make his way into the music world in New York and Los Angeles.

“It’s fun. I don’t know where he’s going with it,” she admitted. Wainwright’s sound is accessible yet, like friend Leonard Cohen’s, “is a little bit out of the ordinary.”

The latest news from Rufus, whom she visits often, is that he may be bound for Hollywood.

“He said, ‘The movies are beckoning,'” McGarrigle said, with a tone of tolerant amusement. “He has a healthy ego.”

For Kate and Anna, shows in New England and eastern Canada beckon each weekend. Along with Kate on acoustic guitar, accordion, banjo and piano, and Anna on electric and acoustic guitar, the sisters will be joined in Camden by violinist Joel Zifkin, Michel Pepin on guitar and bass, and Thom Gossage on drums.

The McGarrigles grew up an hour’s drive north of Montreal with a mother who was part French, and a father who spoke only English. French was the only language spoken at the school the girls attended.

Their father played piano and their mother sang, though mostly Cole Porter and Gershwin, not folk. Though she is Irish, McGarrigle doesn’t like Celtic music, and instead embraced the unique phrasing of French folk music.

In 1980, they released an all-French record, “Pronto Monto,” to critical acclaim.

The McGarrigles have recorded another French album yet to be released. “La Vache Qui Pleure,” which translates to “The Crying Cow,” – a wordplay on the brand of cheese called the “laughing cow,” features lyrics written by friend Philippe Tatartcheff.

“They’re very dark and sad,” she said.

These days, she listens to “heavy-duty, early 20th century” classical music and opera, which “Rufus turned me on to.”

Daughter Martha Wainwright, also a musician, opened for the sisters when they performed in Camden a few years ago. She will join the sisters on a gig in Paris, their first in the City of Lights.

“We’re playing in a Moroccan leather factory,” she said.

The McGarrigle Sisters show features opening act Garrett Soucy of Tree By Leaf. Tickets cost $23, and are available at the Grasshopper Shops in Brewer, Bangor, Ellsworth and Rockland; Mr. Paperback in Belfast; Wild Rufus Records in Camden; Karma Rama in Rockland; and at the door. Tom Groening can be reached at 236-3575 or groening@midcoast.com.