Conjoined, no. But when twins who would otherwise be separate, malnutrition plays a huge part in their development. When they are forming in the womb of a malnourished mother, instead of miscarrying both babies, the stronger of the babies will begin to absorb nutrients from the smaller or weaker twin/triplet/etc. to 'feed' the strongest or more likely to survive. This happens quite commonly and when absorbed entirely, you would never even know.
*edit: Also to point out, nutrition and vitamin deficiency plays a huge parts in how the cells are divided, in example of identical twins when the fertilized ovum separates into two or more. If they do not separate entirely, the result will often be children with multiple limbs.
I do not wish to continue posting in this thread at all, so if you have other points, please feel free to PM.
