Order of Heirship to mineral rights Belmont county Ohio

My husband and I received legal documents in the mail which was a proposal from an oil and gas company, wanting to lease his land or mineral rights, which he had no idea existed that, this land was not inherited by blood, he was the sole caregiver of this elderly man many years ago,who had willed his home,etc over to him, (he had no spouse or children) these documents refered to him as the last known "Heir",the oil and gas company went to great lengths to track him down ,we received a number of legal documents, including deeds dated back to the late 1800s, these documents included an affidavit of "Heirship",My question is IF these are fragmented mineral rights handed down to several family members of the deceased elderly man, wouldn't we have sole ownership being my fiance was the ONLY person mentioned in this will., being the contract says " last known Heir, we assume the rights wouldn't be fragmented., The oil and gas company is offering a lease agreement and 18% royalty, and eager for us to sign, this all happened so quickly, of course we're wondering if there could be a considerable amount of profit owning this, the property is situated in Belmont county, Ohio

Take you time, all oil companies try to get a person to sign real fast hoping to trick you into signing a lease that isn't any good or maybe another oil company will be willing to pay you more for the bonus.

First, I would research you mineral right and see what you own. You may need to find a good oil & gas attorney to do this. I'm not up on Ohio law, so I can't help. Find out who is your neighbors by this mineral and see what they are getting in bonus.