In Episode 4, you will unlock the Legendary Tree bill. Pass it in the Senate to obtain a new evil symbol. This is a strange and unique symbol that allows you to setup a "family tree" of sorts for the symbol's leader. One use for it is to unlock epilogues (See Endings cheat.), but its primary purpose is to grant special effects to the leader by setting relationships. Usually you lose these effects when a member is removed from the symbol's area of effect, but there are ways of making the relationships and their effects permanent:
Leader gains 50 percent stat boost when he/she kills Archenemy: Leader kills Archenemy 10 times.
Leader has 99 percent team attack chance with Comrade: Leader and Comrade team attack together 10 times.
Leader gets 10 percent HP regen when standing side-by-side with Lover: Leader heals Lover 10 times. (Items and magic both OK.)
Leader can use Mentor's spells from anywhere on the map when both are deployed: Leader uses Mentor's spells when standing side-by-side 10 times.
Leader gains 20 percent stat boost when Rival is deployed: Leader and Rival attack and counter each other unarmed or with a Fist-type weapon 10 times.
Permanent Second Cousins
No special effects: Leader and Second Cousin both participate in 10 battles together.
Leader can protect Stepsibling from anywhere on the map: Leader protects Stepsibling from special attacks 10 times.
Leader gains 20 to 60 percent stat boost for wearing the same armor as Twin: Leader and Twin wear the same equipment for 10 entire battles.