What is the ruling on money I receive from renting out shops that sell shisha, now that I have learned of shisha's impermissibility, and how should I deal with my brother in dividing this money?

If the shop is rented for a permissible purpose, but the tenant then uses it to sell prohibited items, the rental contract is valid and the rent money is permissible for you. However, you must enjoin the tenant from selling prohibited items. But if the rental period ends and the tenant wishes to renew the contract to use the shop for selling prohibited items, then this is a prohibited rental.