Enya, 52 (sister to Máire Brennan, 60) The biggest younger sister ever to claw her way out from under her family's shadow. Before she became a multi-platinum solo superstar, Enya was briefly a member of the Brennan clan's act Clannad (pre-"Theme from Harry's Game"), which featured her older sister Máire Brennan, who has a successful solo career of her own but still no "Orinoco Flow (Sail Away)."
Tamar Braxton, 36 (sister of Toni Braxton, 45) Long before she became a reality-TV breakout star (via Braxton Family Values and her own Tamar & Vince) and a member of a The View-style talk-show panel (on The Real, which began a four-week test run on Fox affiliates this month), I was actually interested in what Toni's younger sister had to say -- er, sing. Her 2000 debut album Tamar was just average, but somewhere out there exists a shelved album called Ridiculous (which ended up being reconstructed and reworked into Tamar) that I spent months drooling over in the form of an advance CD in 1999. What's ridiculous is that Dreamworks Records didn't give Ridiculous a shot: It could have been, should have been, one of the best R&B releases from around the turn of the century.
Ashlee Simpson, 28 (sister of Jessica Simpson, 33) Speaking of reality-star singers, I loved Ashlee Simpson at first sight, which was when she waltzed into my office at Teen People wearing a Dolly Parton t-shirt and introduced herself. I took one look at Jessica's then-17-year-old kid sister and wondered, "Why can't Jessica be more like that?" Then a few years later, I heard Ashlee's music and rescinded the question. I didn't care for her early pop hits, but if her recent work ("Bat for a Heart," a 2012 comeback song that may or may not appear on her upcoming fourth album) is any indication of what she can and will do in the future, my Ashlee appreciation might soon bloom again.
Solange Knowles, 27 (sister of Beyoncé, 31) Why can't Beyoncé be more like her little sister? That's the thought that popped into my head last night when I heard Solange's 2012 single "Losing You" -- which flopped, unfortunately -- playing in a Berlin bar. I still haven't checked out any of her other tunes yet, but this one shows promise. Solange sounds so effortless, unpretentious and, most importantly, fun -- everything Beyoncé hasn't been in years.
Louise Mandrell, 59 (sister of Barbara Mandrell, 64) Sure she and Irlene were basically Kelly and Michelle to Barbara's Beyoncé on early '80s TV's Barbara Mandrell and the Mandrell Sisters, but Louise actually had a string of country hits in the '80s and -- surprise! -- some of them, including a 1986 cover of Eric Carmen's 1985 should-have-been-a-hit "I Want to Hear It From Your Lips" (Carmen's original only made it to No. 35 on Billboard's Hot 100, while Mandrell's remake reached the same peak on the country singles chart), show not only impeccable taste in material but unmistakable talent, too.
Crystal Gayle, 62 (sister of Loretta Lynn, 81) It's now 35 years into my love affair with Loretta Lynn's younger sister, and I still can't believe that she's the coal miner's daughter, too.