They will, but their block reward is always calculated as the relative percentage of their harvest power contribution for their harvest club. So whilst they might mint more new blocks being part of a very strong harvest club, they will also receive a small cut of the fee reward due to the strength of all the other harvest club members. Whereas if they join a smaller group, they'll mint blocks left often, but have a high relative slice of the total harvest power, and hence receive a high percentage of the block reward. This is a decision that each user will need to make.

The only sure fire way to increase your own rewards is by increasing your own harvest power.