"well yer course he looks like my father. He only goes back 3 maybe 4 generations" Draco spoke like this was common knowledge. Harry looked at Draco "Isaac Newton?" They were in a museum, because Harry had dragged them into the museum stating "it's my weekend, and I like museums". He'd simply mentioned that the painting of Isaac Newton had a resemblance to Draco's father Lucius.
Draco carried on "We're related via his sister Mary Newton, she later became a Smith. Uncle Issac didn't have kids. He was too busy trying for fame and fortune in the Muggle world". Harry looked at Draco "Isaac Newton was a wizard?". Draco nodded "black sheep of the family by all accounts, he wanted to help muggles by bringing alchemy to them, but he couldn't cos of the statute of secrecy. So he tried for years to bring it to them without magic, or things from our world. He later realised it wasn't possible without magic. So he brought them physics instead".
This was Draco all over, casually dropping some mental piece of information on to Harry.