Kevin is one of the guardian of the Michina Town ruins. He along with Sheena had traveled to many parts of the Sinnoh region to investigate the space-time distortions that the Legendary Pokemon had been creating.
Kevin helped explain the Michina legend to Ash and his friends the day they arrived. He also gave them a tour of the ruins with Sheena.
Kevin seems to be Sheena's boyfriend. When Sheena returned from the past, he quickly went up to her and hugged her, to Brock's disappointment.