Welcome to the forum. Did you mean 14W? 29-20N-14W? You will find many helpful folks on the forum. The first places to start are:
1-Read the Mineral Help Tab above and get familiar with the language.
2- Have the probate documents been finished and filed? He will have to have them filed in the Major County Courthouse.
3-Do you know if there is any production? That leads you in one direction. If no production, then Comanche may be wanting to lease.
4-When you say he received letters, are they from folks that want to buy or from operators that are about to commence activity (yes on Comanche-who has permits for two wells). Comanche has already spud one of the wells, which went south into section 32. If no perforations in 29, then no royalties.
5-Do you have the exact location of the minerals? It should say something like SW4 NE4 of 29-20N-14S or similar. Two wells in the section do have production, so he may have royalties if his acreage is in the spacing of those wells.
Lots to find out.