yo agrupaba
I used to group / I was grouping
tú agrupabas
you used to group / you were grouping
él agrupaba
he used to group / he was grouping
nosotros agrupábamos
we used to group / we were grouping
vosotros agrupabais
you used to group / you were grouping
ellos agrupaban
they used to group / they were grouping