In January 2010, two months after the birth of Martha's son, Kate passed away. Martha had lost her mother at a time when she was only getting used to the idea of having a child of her own.
"It's certainly not how you expect it to happen," says the Canadian-American musician. "I had spoken with my mother for years about having children and I think she was very excited to be a grandmother. But we also knew that her time was limited on this earth, so it wasn't a complete shock."
It was, however, a "tough pill to swallow": the joys of having children combined with the grief of losing a parent.
As Martha explains, "you find help where you can get it" and the famous Wainwright/ McGarrigle family grew closer. Kate's sister, Anna, had always been more than just a sibling. Together, Kate and Anna were an internationally renowned songwriting and recording duo. "It's brought me a lot closer in many ways to my aunt Anna," says Martha, "who has sort of become a surrogate grandmother and mother."
Now 36, Martha doesn't mind getting personal. "For me, it's more interesting to talk about my family, and my mother and her music, than it is to sort of go on and on about songs or my own kind of odd career," she offers. "Being able to talk about my mother is a way for me to keep her in my life."
As for her "odd career", Martha released her first studio album in four years last October. It took a while to get going. "After I was able to pick up a guitar again and the baby was getting bigger and in good health, I was really set on starting my next record," she says. "I was eager to get back out there and to continue working. And I also had a lot of feelings ... "
Returning to the day job is what helped Martha to cope with "new realities". "I knew, even when I was pregnant, that I was gonna try and incorporate, you know, motherhood and my life into how I make a living," she continues. "Because I need to work -- I don't have any other skills, and I feel I have a responsibility to work, so I've always wanted to do both and to not let go of my musical career."
Martha also had a new audience member to cater for -- one whose opinion she now values the most. "When I wrote these songs, my son was still a baby, and now I can see that he's getting older and is becoming more conscious of what I'm saying, I will probably have to be more careful not to embarrass him."
Recorded at Sean Lennon's home studio in New York and produced by Yuka Honda, of Cibo Matto, Martha's third studio album, Come Home To Mama, explores the various ups and downs of the past four years, and features performances from Lennon, Martha's husband Brad and Wilco's Nels Cline.
Its eerie, piano-led centrepiece (the beautiful Proserpina) showcases Martha's remarkable vocal in a way that had previously gone unheard. It's also the last song that Kate McGarrigle ever wrote. "It's made me want to try harder," says Martha, of her mother's passing.. It's made me want to succeed more.
"There's also this new sense of responsibility that comes out of being a parent, and certainly, the need to have some success in an industry that's difficult to have success in. I've become an adult and it's much more necessary to try harder," she laughs.
Martha has had her fair share of success. In 2006, Snow Patrol's Gary Lightbody wrote a song with her voice in mind. The end result was the entrancing Set The Fire To The Third Bar on which Martha featured. She has toured with her big brother Rufus, Pete Townshend and Van Morrison. She's also got the critics on her side.
Of course, you don't talk to one Wainwright without mentioning another. After all, Martha is probably best known for Bloody Mother F***ing A**hole -- an angry guitar tune about her folk-artist father Loudon Wainwright III.
Next month, she returns to Dublin for a two-night stint at the Pepper Canister Church. Hmmm, Martha Wainwright in a church, singing an expletive-laden number about her dad... now that should be interesting. "It is," she replies. "I've done it before. It's always a bit embarrassing. But, you know, luckily we don't live in Russia. And we're not members of Pussy Riot, who have been wrongfully treated ... "
Come Home To Mama is out now. Martha Wainwright plays the Pepper Canister Church on February 3 and 4