I have read online that Obama has said his stepfather was a "non-practicing muslim." He says he father was "agnostic."
Obama claims that his name Barack is Swahili. I must say, it certainly sounds Islamic. I don't know anything about the Swahili language.
Everything in this article appears plausible, although I cannot say for certain.
Swahili, IIRC, is a language largely based on Arabic, so the name Barack is probably Muslim, and a popular name in Kenya since a large portion of Kenya is Muslim.