I got my dog from the shelter and from day one he would follow me around and got possessive and protective of me but not my dad from the first time I locked eyes with him I felt like there was a connection and instead of me just choosing him, he chose me as well, he is also more obedient for me when he knows my dad is the boss, my dad could try and tell him to sit a few times and even then he may not but when I say a command he does it instantly, why would that be?
Your dog has practiced more with you than with your dad. Dogs don't generalize well. The concept that a command means the same thing when not issued by the same person in exactly the same way (and might earn approval/treats) has to be learned.
If your dad isn't available, find other people who can be talked into occasionally helping the dog practice this skill.