Quicksilver

Pietro Maximoff is a speedster and the older twin brother of Scarlet Witch. Pietro was kidnapped from Serbia and brought to Wundagore Mountain, the base of the High Evolutionary. For years, he and his twin sister, Wanda, believed they were the children of a Romany couple, Django and Marya Maximoff, later revealed to be the twins' maternal uncle and aunt. The High Evolutionary supposedly abducted the twins when they were babies and experimented on them. Once he was disgusted with the results, he returned them to the Maximoffs' custody, disguised as regular mutants.