NEW YORK  - Madonna's estranged brother said Monday he doubted she had an affair with baseball star Alex Rodriguez and said she was committed to her marriage to British film director Guy Ritchie. Christopher Ciccone told ABC television the 49-year-old pop star would strive to save her marriage of seven years, amid reports linking her to Rodriguez and speculation the couple will divorce. "First of all " despite everything else, she's still a Catholic girl," Ciccone, who has written a book about his sister, "Life With My Sister Madonna," told ABC's "Good Morning America." "I doubt this is actually an affair," he said, adding that he was "sure" Madonna had nothing to do with the breakup of Rodriguez's marriage. "It seemed absurd to me, truly." The pop legend will "do what's best for her family and her kids," he said. "And I think that she'll do her best to maintain the marriage and keep it going." "She's not the kind of person just to walk away," Ciccone said. Ciccone, who is openly gay, said he was very close to her sister until her marriage to Ritchie, the 39-year-old director of "Lock, Stock and Two Smoking Barrels" who he accused of being homophobic. Asked what happened to his relationship with Madonna, Ciccone said: "Guy Ritchie pretty much happened to our relationship for the most part." "We both really couldn't exist in the same hemisphere. Not to mention the issues, I think, with homosexuality," he said. Madonna took the rare step last week of issuing a formal denial of reports linking her to Rodriguez. Madonna, who was previously married to US actor Sean Penn, is widely regarded as the world's highest-earning female singer with putting her top of its "Cash Queens of Music" earlier this year with earnings of 72 million dollars between June 2006 and June 2007.