4.Maureen McCormick and Barry Williams played siblings Marcia and Greg Brady on The Brady Bunch and dated for a bit in real life — Barry was actually Maureen's first kiss!
5.John Travolta played Diana Hyland's son in TheBoy in the Plastic Bubble, and they began dating in 1976 until Diana's death in 1977.
6.Matthew Broderick and Jennifer Grey played siblings Ferris and Jeannie Bueller in Ferris Bueller's Day Off and started secretly dating while they made the film.
7.Eleanor Tomlinson and Harry Richardson played sister and brother in Poldark and then dated for about a year until their breakup in 2018.
8.Emily VanCamp and Chris Pratt played sister-and-brother duo Bright and Emily Abbott on Everwood, then dated for three years.
9.Maggie Grace and Ian Somerhalder played stepsiblings Shannon Rutherford and Boone Carlyle on Lost, then began dating after their characters were killed on the show.
10.Tamela and David Mann have been married since 1988 but starred as daughter and father in the movie and TV versions of Meet the Browns; they have reprised their role in several Tyler Perry projects.
11.Jennifer Carpenter and Michael C. Hall played sister and brother on Dexter,eloped in 2008, got divorced in 2010, and then continued to play the roles until the end of the series in 2013 and returned for the 2021 revival.
12.Shannen Doherty and Jason Priestley played sister and brother on Beverly Hills, 90210, and years after the series ended, Jason acknowledged briefly dating Shannen along with some of his other costars.
13.Katherine Heigl and Jason Behr played sister and brother on Roswell and got together shortly after meeting on set.
14.Michael Emerson and Carrie Preston have been married since 1998, and Carrie ended up getting to play Michael's mother on Lost all because of a joke.
15.Lauren Graham and Peter Krause played siblings Sarah and Adam Braverman on Parenthood, and after years of trying to keep Peter in the friend zone, Lauren finally started quietly dating him during the run of their show.
16.Tom Hanks and Rita Wilson played siblings in Sleepless in Seattle five years after getting married in 1988.
17.Shane West and Evan Rachel Wood played siblings on Once and Again when Shane was 21 and Rachel was 12. Nine years later, they reunited and started dating.
18.Kirstie Alley and Parker Stevenson married in 1983 and then went on to play siblings on the miniseries North and South: Book II.
19.Will Arnett and Amy Poehler were actually married in 2003, before they went on to play the sibling skating duo Stranz and Fairchild Van Waldenberg in Blades of Glory.
20.Milo Ventimiglia starred as Hayden Panettiere's uncle on Heroes; they began dating during the show's run in 2007 and stayed together for about two years.
21.Drew Barrymore and David Arquette played siblings in Never Been Kissed, and years later David confirmed that the two had dated years before (even though Drew denied it).