There was in interview with Tom Brady in ESPN Boston on playing multiple sports. He didn't play football until high school. Until high school he played soccer from rec ball through middle school. He always played three sports (soccer, basketball and baseball) until high school. In high school he played football and baseball. He was drafted by the Expos. Scouts said he would have been a top five rounds pick had he not been so adamant he was going to play college football.
Then he was asked about his kids. The boys play soccer, basketball and baseball. His girl is too young for organized sports. He said he hoped his kids are physical and athletic late bloomers for two reasons. 1) He wants them to focus on how to play he sports properly to succeed in the long run and 2) He doesn't want them to have to deal with outside influences to specialize before high school.