Grr, to say the same thing again: the person he is writing to and his father are established as two different people even in WCA. His 'father' *was* (past tense) a military officer. It's mentioned in "Recreation" and his 'ghost' is seen in "Expendable".
The man he writes to, who raised him and is alive is someone who is against the war and the military in general ("... I know you disagree with my decision to come here...", in Red & Blue). (It's established in later sources that this is his uncle).