Well, the immediate answer is to hand over the property management to one of them, and tell them to collect bids and assign the job as they see fit.
But the bigger solution is not to co-own rental properties with family members. Actually, I'm of the persuasion that very few business partnerships are actually a good idea, and that it is a wise rental investor who owns their rental properties by themselves.
Maybe the answer is to sell the rental properties and start from scratch, or buy them out, but either way I would urge you to disentangle yourself from business partnerships with family members.
Good luck,
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Brian
Rental Agreement