Share mineral rights with another owner

I own 1/2 the mineral rights for a particular property. The owner of the other half of the rights also owns 100% of the physical property. He (the other owner) has a lease with a gas exploration company. That company has never approached me about a lease, though, I have been approached by another company.

What would happen if the company that is leasing from the other owner finds gas? What are my rights?

Are there any complications if I elect to lease my rights to the other company?

Thanks.

Dear Ms. Fleischer,

A common question. This is too complicated a question to answer here, but I promise to blog about this in the near future and place a link to the blog here.