Recently I was asked a rather unusual and amusing question, summarized below; following is my response.
Gilbert and Anthony are natural, identical twins. Both Gilbert and Anthony have been cloned. For the sake of discussion, Gilbert's clone will be referred to as Gilbertclone; Anthony's clone will be referred to as Anthonyclone.
What is the nature of the relationship, if any, between Gilbertclone and Anthonyclone? Would it be proper to consider Gilbertclone and Anthonyclone twins, since they share the same genetic makeup? What is the nature of the relationship, if any, between Gilbert and Anthonyclone?
The American Heritage® Dictionary of the English Language defines "clone" as "an organism that is descended from and genetically identical to a single common ancestor".
It would be proper to say that Gilbertclone's relationship to Gilbert is that of a clone. It is also proper to say that Gilbertclone is a descendent of Gilbert, though the term descendent is more general, including sons, daughters, grandchildren, etc. Thus the term clone is more specific, and therefore preferred.
It would also not be inaccurate to refer to Gilbert as Gilbertclone's parent or ancestor. The term "parent" is defined as "an ancestor; a progenitor; an organism that produces or generates offspring". Therefore the term is fitting in this case, as it is not limited only to natural birth. The term "father" is also defined as "a male ancestor"; likewise, a son as "a male descendant"; so one could without error refer to Gilbert and Gilbertclone as father and son.
The relationship between Gilbert and Anthonyclone, therefore, is that of uncle to nephew. The term uncle is defined as "the brother of one's mother or father". Since Gilbert and Anthony are natural twins, and therefore brothers, and since it is not innacurate to refer to Anthony as Anthonyclone's father, one may rightfully refer to Gilbert as Anthonyclone's uncle, and Anthonyclone as Gilbert's nephew.
Following the same reasoning, the most proper way to describe the relationship between Gilbertclone and Anthonyclone is that of cousins. A cousin is defined as "a relative descended from a common ancestor, such as a grandparent, by two or more steps in a diverging line." This is clearly the case, because both Gilbertclone and Anthonyclone share the same grandparents, namely, Gilbert and Anthony's natural father and mother. They are, in fact, first cousins.
It is not proper to consider Gilbertclone and Anthonyclone twins on the basis of their shared genetic makeup. A twin is defined as "one of two offspring born at the same birth." To apply this term, one would have to consider the method of cloning. In the case of Dolly the sheep, the nucleus of a cell from the parent was placed in a host egg cell, and implanted into a surrogate ewe, who then gave birth to the clone. In order for Gilbertclone and Anthonyclone to properly be considered twins, they would have to be cloned in a similar manner, and placed at the same time in a single surrogate uterus, and birthed at the same time. (Pity the surrogate!) Incidentally, even so, they would be considered fraternal, and not identical twins, even though they have the same DNA. An identical twin is "either of two twins developed from the same fertilized ovum", which is not the case here. If Gilbertclone and Anthonyclone were birthed at the same time, they would simultaneously be twins and cousins. They could also be considered brothers, but only by virtue of the fact that they shared the same surrogate mother, and not on the basis of their genetic fathers.
Any argument of semantics must necessarily depend on the definitions in use.