Commentary Par XXII 61

This represents the last use of the word 'brother' (frate) as a term of address in the poem.  See C.Purg.IV.127.

See Carroll (DDP Carroll.Par.XXII.61-63) for the notion (attributed only to Chimenz [DDP Chimenz.Par.XXII.61-63] by Bosco/Reggio [DDP Bosco.Par.XXII.61]) that Benedict is gently reproving Dante for having called him 'father' ([Par XXII 58]) by insisting that they are better considered brothers in Christ.  Compare the desire of Pope Adrian V not to have Dante kneel before him in obeisance, since they enjoy a similar brotherhood ([Purg XIX 133-135]).