I had a relative living in her mobile home on my property which is in the State of Alabama. She is now deceased. Can I force her children to move her mobile home? What can I do if the mobile home is so old that it can't be moved?

Is there any written agreement ?

Which of the family now owns it, or is it still in probate ?

You will have to give them written notice to have it moved. If not state penalty in money for not moving. Then if they don't move it, you can do lien on mobile home, and get a repo on it, so that is your issue to remove

If the children have not instituted probate proceedings, they have no obligation with reaspect to the moblie home.