The father of the 5 Browns, Keith Brown, was sentenced yesterday to 10 years to life in prison for sexually abusing his three daughters when they were children. The popular piano-playing quintet did not attend the hearing and sentencing. The Brown girls approached authorities two years ago and revealed their sexual abuse past out of concern that their father, after being fired as the band’s co-manager, was considering taking on new child acts. Brown pleaded guilty to sodomy on a child under 14 and two charges of sex abuse of a child.