Thirteen-year-old Shen Xiaoyan has been in the Shenzhen state orphanage her whole life.

Born with cerebral palsy, she was abandoned by her parents who couldn't afford to take care of her - or didn't want to - perhaps both.

In January this year, knowing that she would turn 14 in August and be no longer eligible for overseas adoption, an American advocacy worker at the orphanage put her picture on a Facebook page for prospective adoptive parents.

The picture was seen by Lisa Lumpkins, a mother-of-six from Kentucky, who has already adopted four Chinese children.

Lisa was immediately struck by how similar Shen Xiaoyan looked to her other daughter Shen Huamei, now called Aubery.

The 43-year-old managed to get permission from the orphanage director to carry out a DNA test and it proved that the two girls were sisters.

Aubery and Shen Xiaoyan, or Avery as she's called in English, had been living at the same orphanage but never knew they were sisters.

The Lumpkins family immediately started the adoption process to reunite the girls.

They managed to complete the process and make Avery part of the family just two days before she turned 14.

We met Avery at the orphanage the day before she was to be adopted and a smile never left her face.

She was looking forward to meeting her new family and to greeting her former friend Aubery as her little sister.

The Shenzhen orphanage is a clean, friendly place where almost all of the 500-plus children are disabled.

We saw many children with Downs Syndrome, cerebral palsy and physical deformities.

The main reason they were abandoned is poverty. In China there's a limited social welfare system and raising a child with additional care needs is very expensive.

The latest estimates show China has more than half a million orphans, with around 20% of them living in one of around 800 state-run institutions.

A decade ago many of the country's orphanages were filled with healthy girls, reflecting the one-child policy and a desire for a son, but now a majority are disabled.

Healthy children tend to be adopted quickly, either within China or by western parents, primarily from the US.

Thousands of Chinese children every year are adopted by Western parents. It's big business and there is a lot of money involved.

There are several adoption agencies who facilitate the adoptions and thousands of pounds change hands for the child, the paperwork and the necessary visa.

The US consulate in Guangzhou is where all families must come to get the necessary paperwork and visas and at our hotel in the city I've seen at least half a dozen parents with their newly adopted Chinese children.

When Avery met her new father Gene Lumpkins this afternoon she appeared happy and a little overwhelmed by all the attention.

There are obvious language and cultural barriers which will need to be overcome.

The teacher who accompanied her from the orphanage told us she doesn't fully understand what's going on, but they are grateful to the Lumpkins for stepping in at the eleventh hour to spare her from a life in care.

Avery will soon be on a flight to America to be reunited with the sister she never knew she had.