How do we handle a sibling, late 50s, who needs to go to the Dr and have CBC and probably needs to be on meds but won't listen to us?

A friend spoke with our sibling, who lives alone and has night job. Confirmed our fears that he appears delusional (also hears voices). He was always obstinate. He won't let us sell our parents estate that was bequeathed to all the siblings years ago. We don't want to go to partition suit. He won't accept any of our advice.

Thank you.