Which preposition to use with adjutor

in Occurrences 2%

Here they made a free distribution of the religious tracts they had taken with them, and found an able co-adjutor in their postillion.

to Occurrences 1%

The Count's success was Fabrice's; that youth found himself established as co-adjutor to the Archbishop of Parma, with a reversion to the Archbishopric on the demise of its worthy occupant.

Which preposition to use with  adjutor