Of all the salacious lyrics that permeated 1980's Dirty Mind, perhaps none were as outrageous as "Sister." For all the controversy that "Darling Nikki" raised thanks to its heroine's public dalliance with a magazine, it had nothing on the second-to-last cut from Prince's third album. Maybe it would have had he been more famous at the time.

On "Sister," he reminisces about how, when he was 16, he got a sexual education from his freewheeling sister, who was twice his age at 32. 'She showed me where it's supposed to go / A blowjob doesn't mean blow / Incest is everything it's said to be," he sings, later adding, 'She only wanted to turn me out / She took a whip to me until I shout / 'Oh, motherfuckers just a motherfucker, can't you understand?'"

Prince had three half-sisters -- Sharon, Norrine and Lorna -- as a result of his John L. Nelson's first marriage to Vivian Howard. Norrine was born in 1942, which means that she was 32 when Prince was 16.

So was Prince just looking to shock people with the most outrageous thing he could think of or was "Sister" autobiographical? While he never came forward with a definitive answer, he told the Los Angeles Times in 1980 that his fascination with sex was a “part of life. It’s something that’s inside of all of us to some degree, whether we like it or not. We may think about it or encounter it in some form or other.”

Then, in 1983, Prince told Musician that, while he could understand if people thought that another particularly lurid lyric on Dirty Mind, "Head," could be thought of as satire, he insisted that “'Sister' is serious. ... All the stuff on the record is true experiences and things that have occurred around me and the way I feel about things. I wasn’t laughing when I did it, so I don’t suppose it was intended that way."

That could have been an example of Prince deadpanning, such as when he told a radio station that "Soft and Wet" was "about deodorant." Or his use of the phrase "things that have occurred around me and the way I feel about things" could simply refer to a bizarre fantasy he had.

Or it could have been a way of maintaining a degree of mystery about his personal life. His next words to Musician were, "That’s why I stopped doing interviews. I started and I stopped abruptly because of that. People weren’t taking me seriously and I was being misunderstood. Everything I said they didn’t believe anyway. They didn’t believe my name. They didn’t believe anything."

A Billboard article about Prince's siblings says that very little is publicly known about Norinne. But we know that Lorna, who passed away in 2006, sued Prince in 1987 for copyright infringement on the grounds that his song "U Got the Look" included lyrics that were similar to an unpublished song of hers called "What's Cooking in This Book?" However, the suit was dismissed in 1988 and her attempt to appeal the decision a year later was unsuccessful.

Sharon Nelson has been involved not only in protecting her late brother's legacy -- she and Norrine tried unsuccessfully to have the contents of Prince's vault remain at Paisley Park -- but also in promoting her father's. She oversaw the recording and release of Don't Play With Love by the John L. Nelson Project, a collection of songs written by her father that she discovered while cleaning out a cabinet. Sharon assembled an all-star group of jazz musicians, including legendary drummer Louis Hayes, and brought them to Paisley Park for the sessions.

Prince's only 100 percent biological sibling is Tyka Nelson, who was born two years after Prince to John L. Nelson and Prince's mother, Mattie Shaw. She's had a music career of her own, with "Marc Anthony's Tune," from her 1988 debut, Royal Blue, reaching No. 33 on Billboard's Hot R&B/Hip-Hop Songs chart.

But she also has a dark past, having been addicted to crack cocaine and working as a prostitute. “I was a single mother and my boys were babies," she said in 2003. "I sold my body for food, money and pampers. I pawned the car Prince had given me and sold the kids’ TV for drugs.” With her brother's help, she entered rehab, and she has since released two albums, 2008's A Brand New Me and Hustler three years later.