My recently widowed mom, 76, was just informed by a social worker 1. that her brother is terminally ill, and 2. he has directed hospice to my mother's home. She was shocked. Can he do this? He's difficult, stubborn and knows my mom is a soft touch. She cannot manage him, which he knows. I believe he's decided that without her husband around, he can just move in and have her cater to him in his final months. The siblings are not close. Mom only sees him when he needs money. The social worker says he is "self neglecting." He refuses to bathe or eat.
Your mom can tell him that if he moves in, she'll kill him.
Sorry for my bad humor.
To answer your question, yes, hospice MUST have your mom's permission. They can't just drop him off at her place. Tell your mom to keep her doors locked and don't answer if he shows up.
No, of course he can't just decide he's moving in with her. Yes, of course it would have been sensible, not to mention courteous, to have asked her before filling in the forms. But she needn't be shocked, just firm. Alternative arrangements will be made for him.
Good luck and Godspeed with a difficult situation