JKR interview 

J.K. Rowling: Yes, Harry and Voldemort are distantly related through the Peverells. Of course, nearly all wizarding families are related if you trace them back through the centuries. As was made clear in Deathly Hallows, Peverell blood would run through many wizarding families.

or another one:

Isabel: Did Bellatrix ever love her husband, or did she have love only for Voldemort?

J.K. Rowling: She took a pureblood husband, because that was what was expected of her, but her true love was always Voldemort.

O.O

J.K. Rowling: I’m very aware I haven’t answered everything… keep an eye on my website, and I’ll try and answer some more questions in due course!

Thanks very much everybody, I’ve had a great time, and I hope I’ve covered some of the outstanding questions (I hear a distant roar of ‘YOU DIDN’T GET TO MINE!’)

That’s it… I’m Disapparating. Bye

Good interview, JK Rowling!

I actually figured out that they were related before reading this... :)