Fraternities can be thought of as religious guilds. They took on mutual support, religious devotion and the financing of church activities. They held masses, organized charity and cared for the upkeep of altars and chapels within the church.

Five fraternities were active in the Old Church; the Brotherhood of Our Lady (founded the old and the Mariakapel), the Hamburger Brotherhood (founded the Hamburgerkapel, dedicated to St. Peter and Paul), the Mary Magdalene Brotherhood (with female members only), the Guild of Holy Sacrament and the Eleventh-Mis Guild.