Los Angeles: Grammy-winning singer Christina Aguilera, mother of two, says her kids are her topmost priority.

Aguilera, who has a seven-year-old son Max from her previous marriage to Jordan Bratman, welcomed daughter Summer Rain last year with fiance Matt Rutler.

The 34-year-old singer, who has returned to 'The Voice' as a coach, said juggling career with motherhood is not easy but Summer and Max come first, reported People magazine.

"They are the center of my universe," Aguilera said.