If you were wondering how Harry Potter got his name, then JK Rowling has finally given an answer. She's also explained how it was that there were no wizarding grandparents to take in Harry after his parents died.
Screencap from Harry Potter and the Sorcerer's Stone (WB)
Rowling has explained a lot about the whole family tree over on Pottermore, including where the family's wealth came from. But tucked into it is a relative of Harry's named Harry Potter:
Henry Potter (Harry to his intimates), who was a direct descendant of Hardwin and Iolanthe, and served on the Wizengamot from 1913 - 1921. Henry caused a minor stir when he publicly condemned then Minister for Magic, Archer Evermonde, who had forbidden the magical community to help Muggles waging the First World War. His outspokenness on the behalf of the Muggle community was also a strong contributing factor in the family's exclusion from the 'Sacred Twenty-Eight'.
The "Sacred Twenty-Eight," in case you're not up on your Potterverse historical lingo, was a 1930s list of the British wizarding families still "truly pure-blood." The Potters, with their Muggle-friendliness and occasional marriages to Muggles, just didn't qualify.
Henry/Harry is the Boy Who Lived's great-grandfather. Henry's son Fleamont — oh yes — had James Potter very late in life and he and his wife died shortly after James married Lily.
This does bring up two questions: a) which one of these characters will be popping up in the Fantastic Beasts movies? Because I bet one does. b) why can't anyone in fiction give their kids names that don't belong to the dead? Or some bizarre family naming scheme? Harry was such a nice, normal name. And now it's also an inherited one. I guess Harry comes by the impulse that gave Albus Severus Potter his name honestly.