Miley Cyrus and Trace Cyrus

(Photo by Kevin Winter/Getty Images)

Luke Wilson and Owen Wilson

(Photo by Evan Agostini/Getty Images)

Haylie Duff and Hilary Duff

(Photo by Frazer Harrison/Getty Images)

Alec Baldwin and Stephen Baldwin

(Photo by Cindy Ord/Getty Images)

Alexis Arquette, Rosanna Arquette, Richmond Arquette, Patricia Arquette and David Arquette

(Photo by Frazer Harrison/Getty Images for AFI)

Venus Williams and Serena Williams

(Photo by Stephen Lovekin/Getty Images)

Mary-Kate Olsen and Ashley Olsen

(Photo by Dave Kotinsky/Getty Images for JCPenney)

Ben Affleck and actor Casey Affleck

(Photo by Claire Greenway/Getty Images)

Britney and Jamie Lynn Spears

(Photo by Frank Micelotta/Getty Images)

Maggie Gyllenhaal and Jake Gyllenhaal

(Photo by Frazer Harrison/Getty Images)

Nick Carter and Aaron Carter

(Photo by Frazer Harrison/Getty Images)

Loretta Lynn and Crystal Gayle

(Photo by Rick Diamond/Getty Images)

Marie Osmond and Donny Osmond

(Photo by Ethan Miller/Getty Images)

Emilio Estevez and Charlie Sheen

Photo credit: Ava V. Gerlitz Showtime

Keenan Ivory Wayans, Shawn Wayans, Marlon Wayans and Damon Wayans

(Photo by Evan Agostini/Getty Images)

Neil Perry, Kimberly Perry and Reid Perry of The Band Perry

(Photo by Rick Diamond/Getty Images for CMT)

Ashley Judd and Wynonna Judd

(Photo by Evan Agostini/Getty Images)

Ashlee Simpson and Jessica Simpson

(Photo by Ethan Miller/Getty Images for Wet Republic)

Nicky Hilton and Paris Hilton

(Photo by Ethan Miller/Getty Images)

Mark and Donnie Wahlberg

(Photo by Andrew D. Bernstein/NBAE via Getty Images)

Kim Kardashian, Khloe Kardashian, Kourtney Kardashian and Robert Kardashian

(Photo by John Sciulli/Getty Images For City of Hope)

Joel Madden and Benji Madden

(Photo credit should read FREDERIC J. BROWN/AFP/Getty Images)

Nick Jonas, Joe Jonas and Kevin Jonas of the Jonas Brothers

(Photo by Kevin Winter/Getty Images)

Ann, John, and Joan Cusack

(Photo by Matt Carmichael/Getty Images)

Drew and Nick Lachey

(Photo by Jeff Gentner/Getty Images)

Taylor Hanson, Zac Hanson, and Isaac Hanson of Hanson

(Photo by Tim Mosenfelder/Getty Images For Live In The Vineyard LLC)

Dakota Fanning and Elle Fanning

(Photo by Charles Eshelman/Getty Images)

Emily and Haley Joel Osment

(Photo by Vince Bucci/Getty Images)