do i have to have the mavin before the bandet
king or cyclops? I have finished booger vill and the castle although I have no idea
how to prove the lost family member to the church.

Bandit king is other side of dragonspire so not sure how he is annoying Ishad Na unless he kwos a super secret way roung the spire.

Cyclops is in area only assecable through booger caves. There are two exits 1 back to were you enter and the other leads out to an area behind the caves (look on the map)

The lost gut quest is in Shruggen castle.

You don't have to have the Mavin before killing the Bandit King, but the only way to get to him without that happening would be to climb the front of Dragon Spire, then go down around it to kill him (that's where he is). I did do this, so I know it's possible (also killed Grue Morde at the same time). So, while not necessary, it's 95% likely that's the way it will work out.