We have made seperate resources & their admins, like in example below

definition user {}

definition group {
    relation member: user
}

definition organization {
    relation r1_admin: group#member
    relation r2_admin: group#member
}

definition resource/r1 {
    relation admin: organization#r1_admin | group
    relation viewer: user

    permission manage = admin + viewer
}

definition resource/r2 {
    relation admin: organization#r2_admin | group
    relation viewer: user

    permission manage = admin + viewer
}