I suppose, that this question is to be individually answered because the
two genetical similarities are quite similar (sorry for my english, two
beers....not american ones). Statistically two brothers should be more
similar than father and son:
Every brother has statistically 50% same autosomal sequences (sequences
from the same chromosome) from father and mother. That equals the 100%
of the paternal part of DNA for each of the brothers.
The difference should come from the X/Y-chromosomes. The male members of
our hypothetical family share their Y -no "plus-similarity" between
father and son... The X-chromosome of our brothers is, again
statistically, 50% identical (no cross over effects considered). So,
brothers are more similar to each other then to their parants (both of
them).
