Not in the actual sequence of genes: if you sequence the genomes of a pair of identical twins every decade for fifty years, you get the same sequence over and over again. But if you sequence the epigenomes of a pair of twins over the course of several decades, you find substantial differences: the pattern of methyl groups attached to the genomes of blood cells or neurons is virtually identical between the twins at the start of the experiment, begins to diverge slowly over the first decade, and becomes substantially different over fifty years.
