New court documents show that Jamie Lynn Spears, Britney Spears's younger sister, is set to become the custodian of the pop star's SJB Revocable Trust.The move comes amid the #FreeBritney movement, in which fans are increasingly scrutinizing the conditions of Britney's conservatorship.Earlier this month, Britney's lawyer told the courts that she "strongly opposed" the return of her father as the head of her conservatorship.Jamie Lynn Spears, the 29-year-old sister of pop star Britney Spears, has