Re: If twins marry twins, will their offsprings be identical?

The short answer is no, they will probably not be identical. 

The cousins would be more closely related than most cousins since their 
mothers and fathers are genetically identical. So while the cousins would 
probably not be identical they would be as closely related genetically as 
brothers and sisters (that is, children who share the same parents, since 
genetically their parents are interchangable).

Remember we each have two copies of each of our genes, one from mom and one
from dad.  These two copies are called alleles.  Identical twins each have 
the same two alleles for each gene but they too got one from mom and one 
from dad so the two alleles for any one gene might not be identical to each 
other.

Now if identical twins marry identical twins each of their children will 
get one allele from mom and one from dad but there is only a 50/50 chance 
of two children getting the same allele of any given gene.  Since this 
would be true for each gene it would be very unlikely that any two 
offspring would get exactly the same set of all the genes.  For the 
offspring of two set of identical twins, the parents are essentially 
interchangable but the moms have one genetic makeup and the dads another.  
The offspring of either family would share from the same pool of genes and 
so the cousins would be as closely related as brothers and sisters but not 
identical.

Cloning,on the other hand, occurs when the entire genetic makeup of one
individual is used to create another.  In this case there is no 
recombination of alleles and the donor and the offspring share all of 
their alleles for every gene (they are genetically identical, like 
identical twins).