Madonna and Guy Ritchie’s seven-year marriage is in such crisis that the singer and her director-husband are discussing a divorce, reports Britain’s Daily Mirror.The star couple, who allegedly live separate lives in their Â£6million London mansion, have been rarely seen together in public over the course of several months, and have grown increasingly distant over the last two years. A close friend disclosed: “They’re obviously sad but they’re dealing with it like grown ups. While they’ll be the first to admit they have a somewhat fiery relationship, above all there’s a deep respect for each other.Things have just run their natural course.”A formal announcement about the marriage is likely to be made at the end of Madge’s world tour, which wraps up in Mexico on November 29.Another source said: “They live like brother and sister rather than husband and wife and thought it best to call it a day. There’s been a lot of speculation about them having furious rows all the time, none more so than because of the children.The couple are parents to Lourdes, 11–Madonna’s daughter by dancer Carlos Leon–own son Rocco, 7, and adopted son David, 2.Adding to their woes is a controversial book by Madonna’s brother, Christopher Ciccone, that supposedly exposes the Material Girl’s exotic sex life and former drug use.In Life With My Sister Madonna Christopher, 47, says his 49-year-old sister’s past lifestyle is to blame for her crumbling marriage.He claims that Madge, who has made no secret of her flings with women, once told him she was a lesbian.An insider revealed: “Madonna is very saddened by Christopher’s behaviour. As far as she’s concerned her brother going public about her is the ultimate betrayal.