Must admit Andy i had thought the same thing when i watched the series.As you have mentioned,Shiro did mention he hadn't seen his dad for a long time.Now with him and Lamia being a similar age he must not have seen his dad since he was a baby!Shiro is 18 in the series yes?He would have noticed Lamia surely if he had still been around his dad when he found the capsule on Mars.So i think working it out that he had not seen his dad since birth WOW what a lousy dad Mr Hagen was then

don't you think!Does this make sense?