Howdy!
Yes -- this was actually something plotted out but never addressed on the show, though you can find a few references to it in the series itself.
The story was going to be that Blair's adopted father, his uncle, was an anti-war senator -- he's described in the series bible (available at the CIC). This is mentioned in the first episode, where Blair writes home about how he knows his 'dad' disagreed with his decision to join the military.
Blair's biological father, though, was a war hero -- and you see his 'ghost' in one episode, which talks about the family's tradition of service. Those two concepts probably don't make much sense without the background that never really got stated properly that the two characters are different people...