My dad 89 has leukemia of the brain and now see my mom and others in our house, mom died 2013.

I agree with others that this is quite common at the end of life, and even more so when the brain is impaired.
Does your Dad currently have Hospice care?
I am so sorry for this diagnosis and dire prognosis.

Is dad on hospice? It's very common for folks at end of life to see deceased loved ones. My uncle was in a coma for 2 weeks when one day he sat upright in bed suddenly, opened his eyes and held his arms up to the ceiling and shouted MAMA! He passed the following day.

Wishing you strength and courage as you manage dad's situation now.

You don't ask a question so I will just say how comforting I'm sure it is to your dad that he's seeing your mom and others who have already passed.
That often happens when one is nearing death themselves, so I hope you now have hospice on board to help you through this final journey with your dad.