Mariah Carey is one of the most famous singers in the world, but when it comes to her family life she prefers to keep things more private.MORE: Michelle Obama and her family left heartbroken after tragic family deathHowever, to mark Mother's Day in the United States on Sunday, the award-winning star took to Instagram to share a rare photo with her eight-year-old twins Monroe and Moroccan.In the picture, the trio posed on a sandy beach, with breathtaking views of the ocean in the background of