Dr. Troyard

Okay, so it is known that Slaine’s father was terrible at paying proper attention to Slaine, right? Well, this is basically how I think it went.

So basically I’m guessing that he has always wanted to study Aldnoah Drives. Maybe it started somewhere when he was a teen. Somewhere in his young adult years (?) he finally started to study Aldnoah Drives and somehow he took a break from it when he fell in love and got married. He got so in love that he actually took a break from his studies/research. Unless she was a scientist as well. But let’s assume she wasn’t. Somewhere around this time Slaine came into this world. I have another headcanon of Slaine's mom having dissapeared so let's also meantion that. She most likely dissapeared when Slaine was 4 years old, I guess. Out of sadness daddy Troyard continued with his research/study and slowly ended up being more and more absorbed by it.

This is when the whole 'taking care of other people' starts.

Being so absorbed by his studies, he slowly paid less and less attention to Slaine. During the time when he was on Mars was the time when he basically ended up neglecting Slaine.

Now, daddy Troyard has faked his death and went back to earth and completely forgot about his son. During the time of the war (mainly at the end), he has heard several things about Slaine. The more he learns about what happens/happend to him the more he gets the feeling that something isn't entirely right. Because of this, he finally realizes how much he neglected his son.