Be aware that the miles/points you earn often are put into one account with restrictions or costs to transfer them...such as to combine with your father's account levels. So your AA miles from your Citi AA card, for example, don't go into his balance and to move them costs which is normally not at a good rate.

if you're both able to obtain individual Amex cards with bonuses ANA has a sweet spot for Japan & Northern Asia awards at 86000 miles (1:1 point transfer from Amex) in Business roundtrip. Getting the Amex Gold Premier Rewards Charge card (current offer 50k points) & Amex Everyday Credit Card (25k point current offer) you would be almost there. The Premier Rewards card has no annual fee for 1 year, 100$/year airline fee refund and no FTF while the Amex Everyday Credit Card has no annual fee at all but does have a FTF.