As part of the BBC's Who Runs Your World series, the relationship between people who rely on each other are being examined. Here, we hear from conjoined twins.
Reba Schappell is a country music singer in the United States. She is a conjoined twin with her sister Lori. The two are conjoined at the left sides of their heads just above the eye, and are connected by bone, tissue and blood.
I have a job singing in show business. Lori, my twin, has to go along with that because it's my career.
When Lori is at home, and we are at home, it's her time. That's respecting Lori in her daily routine. Because I work and she has to go with me.
Reba (left) found singing success in 1996
She's very accommodating, so I accommodate a lot. And if we're not going to be able to tolerate each other, we're going to either kill each other or - well, that's the only other option: killing each other.
I began singing when I was one, but I got my first professional contract in 1996. A year later, I was winning awards for best new female country artist.
When I am singing, Lori is like any other fan, except she's up on the stage with me.
I run my world the best way I know how with help from my colleagues. But basically, most of the time I do run my world.
Being a conjoined twin, does not really run my world. It's part of our world, but it doesn't run it.
Lori Schappell is Reba's sister.
Our brains our completely separate, we have each a full functioning brain - I don't want to say we each have two brains!
We were born in the Reading Hospital in 1961. We were then put in this institution, which was very unfair. Our parents didn't want it at all. They were against it, but the courts ruled that they wouldn't be able to take care of us. So we were taken to an institution in Hamburg.
We left there; we went to college at the age of twenty.
But they labelled us mentally retarded - you had to be labelled that to be able to live there. But, we were not retarded in any way.
When Lori is at home, and we are at home, it's her time. That's respecting Lori in her daily routine
When we left the institution, we went to live in a dorm. When we got there I was hysterical, just was a mess. Reba had to calm me down and tell me it was okay - that it was good that we were out. She was happy, elated.
Reba and Ginny Thornburgh, who was the wife of the former governor of Pennsylvania, got a whole group of people together and they had this meeting to get the words 'moderately retarded' off of our records.
After we graduated, we moved to an apartment in west Reading, and I took care of the house. I do the grocery shopping and run the household - that's what I'm really smart at.
I do not ask for anything from Reba - I don't get in to her concerts free just because she's a conjoined twin.
I have to pay, just like every other fan that comes to that concert.
They don't see me there. It's like there's a blanket over me because I am quiet and I don't make a noise. They're not hearing the conjoined twin, they're hearing Reba, and they're involved in listening and watching Reba, the performer.
Reba is not me and I am not Reba. I have some friends that I made when we were little. We'll go out together and when we're together, Reba either takes something to read or she'll take one of her scripts along and read that.
It's like we're not there. She can block anybody out, totally.
Do I run my world? Yeah, I do run my world. It's my world. If I don't have any say in it, then it's not my world.
I run Reba's world more than she runs mine. I'm bossy. But, she doesn't run mine.
Being a conjoined twin does not run my world either. I don't wake up every day and say, 'Oh my goodness, I'm a conjoined twin, what does the twin part of me want me to do today?'
I don't even ask it what it wants to do. If I don't want to do it, I'm not going to do it, whether it wants to do it or not.