Auma Obama, 2007.   (Photo: AP)

Obama: It’s Complicated
Due mostly to his father, who had children by four women, Obama has seven living half-siblings (one he had never met died in 1984). He’s tight with two of them. The first is Maya Soetoro-Ng, his younger half-sister, the child of Obama’s mother and Lolo Soetoro, her Indonesian second husband. Maya stayed with Obama’s mother after she divorced Lolo, and she has recently taken time off from teaching high school in Honolulu to make appearances at her brother’s campaign stops. The second, Auma Obama, is Obama’s older half-sister, the child of Barack Sr. and his first wife in Kenya. Obama and Auma first met when Auma visited America after their father died in an auto accident in 1982. “I knew at that moment, somehow, that I loved her … Even now I can’t explain it; I only know that the love was true, and still is, and I’m grateful for it,” Obama wrote in Dreams From My Father.

McCain: Occasionally Useful
The McCain siblings—John, younger brother Joe, and older sister Sandy—are a close-knit crew, but McCain rarely brings them into the spotlight, because, as a campaign aide once put it, "he’s not Al Gore." "We were all basically on the same side of the fence [politically]," Joe, who has worked on McCain's campaigns, has said of his family, "but it was like Talmudic scholars arguing about a single word or an adjective in the Testament." McCain’s siblings are suspiciously absent from his books, but they appear to have been close as children. Growing up, Joe idolized his older brother, referring to John as “my hero of heroes.” Distraught by his brother’s capture by Vietcong in 1967, Joe stopped worrying once he found out John was still alive, "because I knew he was indestructible." The 66-year-old dinner-theater actor and former reporter is vocally pro-Israel and occasionally stumps for his brother, but otherwise keeps a low profile. Sandy, who was diagnosed with breast cancer in 1998, took a rare step into the spotlight to defend her brother when he was accused of underfunding breast-cancer research by George Bush's campaign in the 2000 election.