«أَرَى قُرْبَهُ قُرْبَى»
I regarded being near him as a kind of kinship.
Qurb is nearness; qurbā suggests kinship or a special bond. Their shared sounds and roots allow physical closeness to become an image of emotional relation.
The line does not establish that Abū Zayd is biologically related to al-Ḥārith. It expresses how intimate and valuable the friendship feels.