If he is competent there is little to nothing you can do. Check with his doctor. If the doctor will state that your father needs assistance in managing his affairs you can file to become his Guardian and Conservator. This would give you the authority to manage his affairs. The loans could be deemed to be gifts by Medicaid (if the need arises) unless they are properly documented.
The only other option is if they borrowers are taking advantage of his diminished (but not incompetent) state of mind to the point of breaking the law. That would likely be very difficult.
I suggest the doctor is the best and quickest route to a solution or an answer.
You'd need to address this question to lawyers in Alabama. I am not sure Texas would have jurisdiction for an adult guardianship since he lives out of state. Here is some information on Texas adult guardianships, but again, you need to call some lawyers in Alabama and see what your options are. http://www.dads.state.tx.us/news_info/publications/brochures/pub395-guardianship.pdf
Robert Guest is a Kaufman County Criminal Defense Lawyer with offices is Forney, Texas and Rockwall, Texas. My use of Avvo is not intended to form an attorney-client relationship. Avvo is a limited forum and should never be used as a replacement for a consultation with a local lawyer. My answers are not legal advice. You really need a consultation with a local attorney.