Once, in college, I was watching the Miss Universe pageant with a friend. When they announced Miss Trinidad and Tobago we both turned to each other and simultaneously said, in a complete deadpan tone, “Siamese Twins.”
We then laughed our asses off for about 10 minutes.
Yes, we were drinking heavily at the time.
Quoth Elendil’s Heir:
I think that conjoined twins are probably rare enough that we can’t make meaningful statements about “most conjoined twins”.
EDIT: addicted, what difficulty would you anticipate in them marrying two separate people? One says “I do” to one gentleman, and the other says “I do” to a different gentleman. That’s one of the few aspects of their life that wouldn’t have to be different from normal.
This made me laugh. With all the obstacles they have to deal with in their everyday lives, I kind of doubt this even pings their radar. 
I’d bet they’d just take a cab.
Come to think of it, do they have to pay for one or two airline tickets?