Is it considered elder abuse for his caregivers (my brother and sister in law) to alienate him from me and my family?

They resent me very much and coach dad into saying hateful things and telling us we're no longer welcome in his home. Dad is 86 with alzheimers. Though he does not remember it minutes later, it upsets him at the time and he remains "competent" on paper so that's also a concern. What are the legalities here?