ajpirc, it can get very confusing, but I can at least give an idea from my "spiritual" Order, the Dominicans. There are three levels to this family of St. Dominic:
- Fraternal/co-operator brother
- Third Order/laity
Not every Dominican in history was ordained a priest, though their Order is more priest-oriented than the Franciscans. Most Dominican saints were ordained, such as Albertus Magnus, Thomas Aquinas, and the Holy Father of the Order himself. Naturally the sisters are never ordained, and next to them you have the brothers (called "co-operator brothers" today) such as St. Martin de Porres. The laity take part in the charism of the Order by receiving a small habitual scapular, and go into formation to preach and live in the mode of sainthood. The Order is united more by preaching and theological inquiry than by rank, status, or intimate familial, poor, Franciscan-like bonds. ;)
A "brother" may be a monk, friar, or cleric regular. Different sorts of brothers do different things. I don't know if Canons have a brother-rank.