Celebrities work long days and nights while shooting television shows or movies. It comes as no surprise when costars begin dating one another, but it does seem a little weird when the couple plays brother and sister on their show. Here are the cases of sibling love gone too far.

Chris Pratt and Emily VanCamp
Chris Pratt and Emily VanCamp
Chris Pratt was a waiter before being discovered in 2000. In 2002, he received his first large role in the WB television show "Everwood." It was there that he met his then girlfriend Emily VanCamp who is now known for starring in ABC's "Revenge." VanCamp was cast as Pratt's TV sister, and the relationship distressed some viewers of the show. The couple broke up in 2006 and Pratt went on to marry Anna Farris in 2009.
Milo Ventimiglia and Hayden Panettiere
Milo Ventimiglia and Hayden Panettiere
Their characters weren't siblings in the show "Heroes," but rather uncle and niece, which is much creepier. Despite that and their age difference, the two actors began dating a year into the show. Maybe they bonded over having hard-to-pronounce last names?
Evan Rachel Wood and Shane West
Evan Rachel Wood and Shane West
Before they made it big in the movies, Evan Rachel Wood and Shane West starred as a brother and sister in "Once and Again," a 3-season ABC show that ended in 2002. While they weren't dating while filming, the two did have a fling in 2009 before she went back to Marilyn Manson.
David Cassidy and Susan Dey
David Cassidy and Susan Dey
These two actors played siblings Keith and Laurie Partridge on "The Partridge Family." Reportedly, they were dating for a bit while the show was filming, but they haven't remained friendly. Cassidy dissed Dey in his 1994 autobiography, and Dey refused a 2010 cast reunion because of him.
Michael C. Hall and Jennifer Carpenter
Michael C. Hall and Jennifer Carpenter
Michael C. Hall and Jennifer Carpenter met while filming the television show "Dexter." Carpenter played Dexter's sister Debra Morgan, a detective for the same department. Hall and Carpenter began dating in 2007 and married in 2008. In 2010, the couple announced they were separated and finalized the divorce late 2011.
Ian Somerhalder and Maggie Grace
Ian Somerhalder and Maggie Grace
Ian Somerhalder and Maggie Grace were cast as brother and sister plane crash survivors for one season on ABC's "Lost." After, the couple dated for a year before going their separate ways. The two were reunited for the ten year reunion of the show and reportedly remain good friends.
Lauren Graham and Peter Krause
Lauren Graham and Peter Krause
Lauren Graham and Peter Krause met in 1995 after Graham moved to L.A. They remained friendly throughout the years but never dated until they starred together on NBC's "Parenthood." The couple has nearly five years of dating as of 2014 but have made public statements that there are no plans for marriage yet.
Matthew Broderick and Jennifer Grey
Matthew Broderick and Jennifer Grey
Matthew Broderick and Jennifer Grey dated while filming "Ferris Bueller's Day Off" in 1985. The couple kept their relationship off the public radar until 1987 when they were involved in a deadly car crash in Northern Ireland. Grey took a break from acting after the accident. Broderick married Sarah Jessica Parker and Grey married Clark Gregg in 2001.
Katherine Heigl and Jason Behr
Katherine Heigl and Jason Behr
Jason Behr first appeared in the alien drama "Roswell," on which Katherine Heigl was cast as his alien sister. The couple dated during the course of the show, but the romance ended. Behr married KaDee Strickland in 2006 and Heigl wed Josh Kelley in 2007.
Jason Priestly and Shannen Doherty
Jason Priestly and Shannen Doherty
Jason Priestly and Shannen Doherty played the Walsh siblings on the popular original "90210." The two began dating, but the relationship fizzled out. Priestly went on to marry Naomi Lowde in 2007 and Doherty has been married a few times. Recently, she has gone on the record disagreeing with Priesley's account of her in his memoir.
Maureen McCormick and Barry Williams
Maureen McCormick and Barry Williams
Marcia, Marcia, Marcia! Maureen McCormick and Barry Williams played brother and sister on the iconic TV show "The Brady Bunch" from 1969 to 1974. Williams played the oldest brother Greg while McCormick was the oldest sister Marcia from a blended family. The kids on the show portrayed a loving family who got into the occasional hijinks. However, rumors of wild behavior off set ran rampant. McCormick wrote a memoir in which she discusses her relationship with Williams as well as a few other celebrities.

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