It’s kind of tragic how Ben Reilly died thinking of his niece who he would never get to meet and who would never get to hear about him because she was stillborn.
However in the MC2 universe May Parker was allowed to grow up and when she becomes Spider-Girl it’s Ben’s costume she wears and it’s his web shooters she puts on, in a way Mayday is Ben Reilly’s legacy as much as she is Peter’s.
It’s also bittersweet that despite never meeting each other they always thought of each other. Ben always protected and cared for MJ when she was pregnant (and even before she was pregnant I might add) and worried about her baby’s health. Ben also anxiously awaited baby May’s birth as much as her parents did. Mayday occasionally thinks about her Uncle Ben, she asks Peter questions about him (even if Peter hasn’t told her the entire truth) and despite not having known him she considers him a hero and thinks fondly of him, she even gets upset with Kaine when she finds out he used to torment Ben.
Also Ben’s other legacy, his unknown to anyone but Kaine son, Reilly Tyne protects and guides her as the vigilante known as Darkdevil.
So yeah despite never meeting the bond between this Ben and May is a strong one.
Panels from Spider-Man vol 1 #75 and Spider-Girl #44