Advisory help

My brother faced an RTA (road traffic accident) 2 and half years ago.  He had severe brain injury on his left hemisphere of brain. As a result his right part of the body was paralyzed. We continued the PMR (Physical medicine and rehabilitation) from more than 2 years and now his half of the right hand side is functioning properly. He is able to move his leg on command and raise his hand to a little extent on command. The sad part is he is behaving like a kid and not regained his memory. He is able to recognize his parents and me. He can repeat (speaking) few words on request like (hello, good morning). I can upload his CT scan repots if required.
I am the younger brother at the age of 20 and do not have any medical knowledge. Can you suggest me what can be done for his better treatment?  Is there any operation can be done so that he can regain his memory?  I am more concerned about his memory than anything else.