Are you a twin? No, well are you sure?
You could be a twin, but the twin is within, or a chimera.
The Lion-Goat-Dragon You
A chimera is a mythological beast with the head of a lion, the body of a goat, and the tail of a dragon. However, in biology a chimera is an organism made up of two distinct genetic lines.
It's what happens when twin embryos fuse in the womb. The fusion results in what looks like a single embryo, but the genetic material from each twin remains separate.
What does that mean? Does a chimera have one arm from one twin and the other arm from the other twin?
A Liver From A Different Life
Well, it's something like that. It's not like the arms would look different, exactly, or that the body's organs wouldn't be compatible or not work properly.
However, they do contain different and distinct sets of chromosomes. If you're a chimera, your liver could be composed of cells with one set of chromosomes while your heart, say, consists of cells with an entirely different set.
"Chimera (Genetics)." Wikipedia. Re-accessed for re-run on July 30, 2018.