Justin Timberlake's kids keep him busy. After Lance Bass called out the 40-year-old singer for being slow to respond to texts, Timberlake jokingly said Silas, 6, and Phineas, 1, the two sons he shares with wife Jessica Biel, were the cause.Timberlake and Bass, along with Chris Kirkpatrick, JC Chasez and Joey Fatone, were members of '90s boyband *NSYNC.