Starting with the most obvious to make the list, Michael C. Hall and Jennifer Carpenter.
The idea of relatives dating may gross you out (and it should), but what happens if you're an actor and you fall in love with your co-star -- who happens to be playing your character's relative?
It's happened more often than you might think! For example, Michael C. Hall from 'Dexter' was married to Jennifer Carpenter, who played his adoptive sister, from 2008 to 2011. Creepy!
Lauren Graham and Peter Krause
Lauren Graham plays Sarah Braverman, sister to Peter Krause's Adam Braverman, on 'Parenthood'; but they are a couple in real life. Fortunately for the show, they are able to tone down their chemistry to a more brotherly-sisterly level during filming!
David and Tamela Mann
Tyler Perry's 'Meet the Browns' may seem like a harmless family show, but things are quite a bit different behind-the-scenes! David and Tamela Mann, who play Mr. Brown and his daughter Cora, are married in real life.
Milo Ventimiglia and Hayden Panettiere
These two lovebirds played uncle and niece on the NBC superhero drama 'Heroes' while dating in real life. Maybe they bonded over their difficult-to-spell last names!
Amy Poehler and Will Arnett
This ex-couple had been married for quite some time before they played members of an incestuous sibling ice skating team in 'Blades of Glory.' At least knowledge of their genuine relationship makes their on-screen shenanigans easier to swallow!
Jennifer Grey and Matthew Broderick
After playing brother and sister in 'Ferris Bueller's Day Off,' Jennifer Grey and Matthew Broderick dated. Though they had been hiding their relationship, it became public when the pair were involved in a major car accident in Northern Ireland.
There's more at the source
I don't know why, but I always forget Milo and Hayden used to date...Actually sometimes I forget Heroes happened all together. So, you guys, who do you think is missing from this list?