The adjective irenic describes something that is peaceful. Although you and your sister constantly fought as young children, your relationship might become more irenic as you grow older.
The word irenic is from the Greek word eirēnē, which means peace. Eirene was the Greek goddess of peace. She was one of the Horae, or Hours, and she also represented the season of spring, so she is often depicted holding a full cornucopia. Today, the adjective irenic still maintains its peaceful meaning, and governments are continuously searching for irenic solutions to world problems.