They say that all pure-blood wizarding families are related. The Potters are pure-bloods and so are the Malfoys; so, are Harry and Draco related?
In 2005, J.K. Rowling drew a copy of the Black Family Tree for producer David Heyman. It shows us that Draco's first cousin, three times removed had married a "Charlus Potter". Nothing more was ever said about this Charlus Potter, but unless this is another one of Rowling's fiascos, we can probably assume he's related to Harry.
They are likely related in many other ways as well, seeing as both the Malfoy's and Potter's were pure-blood families.
“The pure-blood families are all interrelated,” said Sirius. “If you’re only going to let your sons and daughters marry purebloods your choice is very limited, there are hardly any of us left.
Harry Potter and the Order of the Phoenix - Chapter Six
Also, as Ailuropoda melanoleuca points out, "Harry's godfather Sirius is cousins with Draco's mother", though that's not a genetic relation.