"I got really scared, I'm like, how do people do this?" Aguilera, who shares 11-year-old Max Liron with former husband Jordan Bratman and five-year-old Summer Rain with fiance Matt Rutler.
"'Cause I know kids need routine and structure -- like bedtime and order. And, how are you supposed to do that whenever you are in different time zones almost every night, and things are changing?" she continued.
Clarkson agreed and said "It's so hard." she shares daughter River Rose, 5, and son Remington Alexander, 3, with husband Brandon Blackstock, as well as daughter Savannah, 18, and son Seth, 12, from Blackstock's previous marriage.
She added that when she first had children, she "cried almost every night".