It's normal for grandparents to give their grandchildren gifts.
Frank wants to give his grandson a gift, but he's afraid his son will steal it.
Frank wants to decide whether to give his grandson a gift.
Frank gives his grandson gifts and points out [so that is son hears] that he'll be asking later what he's done with the gift.
Frank decides not to give his grandson a gift since he doesn't want his greedy son taking it.
Frank keeps checking if his grandson still has the gifts so his son can't take them without his knowing.
To his grandson it appears that Frank is the unfair one since he's never giving any gifts out.