medical exp for parent

[grandmabee]

parent has income of pension 7600 yr and SS of 12,000 yr. monthly medical exp is 4,500 four kids provide balance of support. so together they provide over 50% support. So can the one son claim 1/4 of medical expense for can he claim 100% of medical if they file the multiple support agreement. He can't claim mom as dependent. but what about the medical