"Christ in his mercy . . . did not wish to be alone as the Son"

"As for our being the brothers and sisters of Christ, we can understand this because although there is only one inheritance and Christ is the only Son, his mercy would not allow him to remain alone.  It was his wish that we too should be heirs of the Father, and co-heirs with himself."

     St. Augustine, Sermon 72A.8 (417/418), as trans. Liturgy of the hours for the Feast of the Presentation of the BVM.  WSA III/3, trans. Edmund Hill (1991), 288.  Latin from Miscellanea Agostiniana 1 (1930), 163 ll. 13-16 (155-164):

I can understand brothers, I can understand sisters; it's because there is one inheritance, and therefore Christ in his mercy, while being the only Son, did not wish to be alone as the Son, but wished us to be heirs of the Father, his own fellow heirs. That inheritance, you see, is such that it cannot be reduced in value by any number of co-heirs.

fratres intellego, sorores intellego: una est enim hereditas; et ideo Christi misericordia, qui, cum esset unicus, noluit esse solus, voluit nos esse Patri heredes, sibi coheredes.