I know a compulsory pooling can be required, but it requires a hearing and costs time and money. Since in this case the un leased interest constitutes 33% of the total mineral ownership in the tract, it would likely not be granted or a arbitration would be required. I am not suggesting not to sign a lease, just to require a drilling commitment with a time frame for completion stipulating that the entire drilling unit (if possible for the formation in question) be on the 3 brother's minerals so that they enjoy all the royalty revenue.