They both know their goals and won't let any thing abstruct them in getting there, driven and often too serious.

They're both determined, focused, hardworking, and serious. Also, they both feel that they need to make their fathers proud.

You already said it for me

Both lost their Father and are desperate to make them proud, extremly determined, hard working, and both need to "let their hair down"...figuratively and literally!

Both difficult to get to know at first, but once you do, they're genuinely awesome. :3 Also very devoted to their fathers, etc.