The affix kan comes in the sense of 'he is their leader' after a word in the Nominative 1st-Case with the force of Genitive 6th-Case.,
The word ग्रामणी means 'head-man, leader, spokes-man'. Thus देवदत्तो ग्रामणीरेषां = देवदत्तकाः, यज्ञदत्तकाः ॥
Why do we say 'when meaning a leader'? Witness देवदत्तः शत्रुरेषाम् ॥ Here there is no affixing.,