Sandra Bullock adopts daughter Laila as a sister for Louis

Speaking to People magazine, the Gravity star said she began fostering Laila almost three years ago. Photo / Getty

Oscar-winning actress Sandra Bullock has adopted a second child - a three-year-old girl - from foster care as a sister for her son Louis.

Speaking to People magazine, the Gravity star said she began fostering Laila almost three years ago.

The baby girl had been placed in foster care in Louisiana.

"When I look at Laila, there's no doubt in my mind that she was supposed to be here," Bullock, 51, told People.

"I can tell you absolutely, the exact right children came to me at the exact right time," added the actress, who adopted son Louis, now five, from foster care in New Orleans in 2010.

"My family is blended and diverse, nutty, and loving and understanding," she told the magazine.

"That's a family."

Bullock said she had pledged to keep the long adoption process secret to protect Laila's privacy.

Earlier this year she had publicly denied reports that she had made another addition to her family.

Bullock, who is dating photographer Bryan Randall, first revealed she had adopted Louis about two months after winning the best actress Oscar in 2010 for her role as a woman who takes in a homeless black teen in The Blind Side.

But the career triumph was swiftly followed by a crisis in her personal life when her then-husband Jesse James was reported to have had numerous affairs during their five-year marriage.

Bullock filed for divorce weeks later.