As pointed out, Sirius Black was actually Draco's first cousin once removed - not his uncle. That being said, according to J. K. Rowling, yes, Harry Potter and Draco Malfoy are related - albeit distantly - by marriage, if not by blood. The Malfoys are related to the Weasleys through the Narcissa and her descent from the House of Black. We know that Ron and Draco are fifth cousins once removed. If Weasley is Sirius' second cousin once removed and if Sirius had had a child, that child would be the Weasley children's third-cousin, once removed. Through Hermione's marriage to Ron, and through Harry's marriage to Ginny, Hermione became his sister-in-law. She was also an aunt to his children and the godmother of his oldest son, James Sirius Potter. Harry also had a niece, Rose Weasley and a nephew, Hugo Weasley, through Hermione's marriage to Ron. Which means She’s related to Harry now and harrys related to draco who is related to ron