Don't forget about their mother, too. It would be cool if their parents are shown eventually, but most of the characters of Suikoden either don't have one parent to be seen, or don't have both. There are some exceptions, however. I doubt highly that we'll ever see Odessa and Mathiu's parents.
"And as for the the end of the World, you need not worry. No one should worry about such a thing right now..."
-Leknaat, Suikoden IV