The couple says their 22-month-old boy is "amazing" but they are facing a tough time as "he's hitting his terrible twos a little early", reported FemaleFirst.
"He does not want the diapers changed. He's hitting his terrible twos a little early, so we're hoping he'll get out of them a little early," Timberlake said on the Oscars red carpet.
While Biel said, "He's doing amazing, but it's one of those things where you're like, I love you, but I don't know if I like you."
The "Sexy Back" singer appeared for the first time at the Academy Awards, where he opened the show with a performance of 'Can't Stop the Feeling' from "Trolls".