Dominant Phallus

His control of others is based in his overly large genitals. If his cock is visible and an individual recognizes that it is larger than their own or their significant other's, they will become extremely aroused and open to suggestion.

If the person is not in a relationship, then it is the father figure's penis that determines the control. Knowledge of that person's size is not necessary, so long as they believe the mind controller's cock is bigger then the power works on them.