SAN FRANCISCO
10/31/2011 03:54 pm ET | Updated Dec 31, 2011

Angelina And Angelica Sabuco, Conjoined Twins, To Be Separated At Stanford Children's Hospital (VIDEO)

In a lengthy and complicated surgery expected to last up to nine hours, two-year-old conjoined twins Angelica and Angelina Sabuco will be separated at Lucile Packard Children's Hospital in Stanford on Tuesday.

The Sabuco girls were both with a connected sternum, and their livers and diaphragms are "tightly fused together," according to Bay City News. They have individual ribs, hearts and digestive systems.

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More than 20 doctors and nurses will participate in the complex procedure. "This is a major operation, but we really expect both twins to survive and do well," pediatric surgeon Dr. Gary Hartman said. Dr. Hartman told NBC Bay Area that separating the girls' livers will be the most dangerous undertaking, as the risk of blood loss is high.

Born in the Philippines and currently being raised in San Jose, the twins still express very different personality traits despite their physical proximity, according to their mother, Ginady Sabuco. Sabuco first learned about her daughters' condition when she was seven months pregnant.

"I was asking God: why us, why me?" she told NBC Bay Area. "I want them to live normally, like other children."

According to NBC, most conjoined twins do not make it past pregnancy -- the survival rate is approximately 25 percent worldwide. This will be Dr. Hartman's sixth such operation.

The Sabuco girls are expected to spend four to five days in intensive care and another week in a regular hospital room before beginning to make a full recovery.

"I hope that when they grow up, they go to school, graduate and get stable jobs," Sabuco told Bay City News. "I want them to have a good future."

Take a look at a video of the twins at home below: