The details that I remember are a bit vague, so may not be 100% correct, but the scene I vaguely remember:
Some kind of sexual crime (maybe rape??) is committed and a married man (probably along with other men??) has to give a sample to clear his name. He does so and he's cleared.
Sometime later, he announces to the world that his wife is pregnant. However, one of the guys that was involved in the rape investigation (possibly a close friend of his??) confides with the married man and tells him that he's sterile - which he was obviously blissfully unaware of. The married man investigates further and uncovers a web of lies and deceit .....
the one I was t
thinking of was with the younger partner of it shouldnt happen to a vet
who was sterile
and also had had a bone marrow transplant
to explain the funny DNA profiles