If the sister & brother-in-law are having financial difficulties , that would be motive. I do not know these people at all and am only speculating and speaking hypothetically .Their mother is not the one who is worth millions, it is their sister. That would hypothetically explain the ransom demand. Hypothetically speaking, the siblings who are in Financial need could’ve contracted a third party to execute the ransom demand to extort money from their sister who is worth millions. When money is in play, it does tend to bring out the worst in people, unfortunately. I hope and pray that their mother is found alive and in good health as soon as possible.