  Sieves are constructed for twin primes in class I, which are of the form
2m+/-D, D>=3 odd. They are characterized by their twin-D-I rank m. They have no
parity problem. Non-rank numbers are identified and counted using odd primes
p>=5. Twin-D-I ranks and non-ranks make up the set of positive integers.
Regularities of non-ranks allow obtaining the number of twin-D-I ranks. It
involves considerable cancellations so that the asymptotic form of its main
term collapses to the expected form, but its coefficient depends on D.
