Dduction u/s 80 dd

For section 80DD deduction, only individuals, or a spouse, son or daughter (or any child), parents as well as brother or sister i.e. any siblings can be considered as your disabled dependant, but not Uncle or chacha.

For the purpose of Section 80DD Dependent means:

for individual - spouse,Children,parents,sisters,brothers of the individual or any of them 

In your case as Chacha will not under the purview of Dependent under Section 80DD any maintenance including medical expenditure incurred for him cannot be claimed as deduction. 

IT IS NOT POSSIBLE THAT WE CAN CONSIDER HIM UNDER THE CATEGORY OF PARENTS.

AS CHACHA HAVE NO CHILDREN. HE IS WHOLLY DEPENDENT ON US & WE ALSO CALLED HIM CHOTTE PAPA.

IF NOT U/S 80 DD IS THEIR ANY OTHER SECTION IN WHICH WE CAN CLAIM DEDUCTION FOR HIM.

"AS CHACHA HAVE NO CHILDREN. HE IS WHOLLY DEPENDENT ON US & WE ALSO CALLED HIM CHOTTE PAPA."

Yes in that case you can claim deduction us.80DD, subject to fulfillment of its conditions.