"We do have very normal lives,” says one of Schappell conjoined twins, who are celebrating their 50th birthday

From FOX News:

The world's oldest living conjoined twins have defied doctors' predictions and reached their 50th birthday.

George and Lori Schappell, who are joined at the head, celebrate their special day Sunday.

And the pair is marking the landmark birthday with a trip to London.

Remarkably, the twins are able to live very different and separate lives, with Lori having had relationships and George, who was born Dori and later changed her name to Reba — deciding to live life as a man.

"When we were born, the doctors didn't think we'd make 30, but we proved them wrong,” Lori said. "We have learned so much in the last 50 years and will continue living life to the full."

While Lori, who is 5 feet, 1 inch, was born able-bodied, 4-foot-4-inch George suffers from spina bifida, which has caused severe mobility problems.

As George cannot walk, he sits in a wheelchair-type stool which Lori pushes so the two can move together.

"Most people don't believe us but we do have very normal lives,” George said.

The twins, from Pennsylvania, were born sharing 30 percent of their frontal lobe brain tissue and critical blood vessels, meaning they cannot be separated.

"I have known from a very young age that I should have been a boy,” George said, who began living as a man four years ago. "It was so tough, but I was getting older and I simply didn't want to live a lie. I knew I had to live my life the way I wanted."

Although the pair are both single, Lori has dated men.

Throughout the 1990s, George had a successful music career as singer Reba Schappell and won an LA Music Award for Best New Country Artist.

The famous pair have been the subject of television documentaries, appeared on talk shows and even made a cameo appearance on the TV drama series “Nip/Tuck.”