Which preposition to use with boyars

for Occurrences 1%

He accordingly convoked a meeting of the bishops and boyars for the purpose of asking their advice; but their counsel was even still more conclusive; and the reluctant Prince was compelled to rejoin the army.

on Occurrences 1%

The boyars on the Volga and some of the Pechenegian princes embraced the gospel of salvation together with his subjects, and rejoiced to be admitted to holy baptism.

Which preposition to use with  boyars