I have a question about my nephew's ssi & medicare?

ok well my nephew has cerebral palsy and back in june of 2005 my brother-in-law ped away. Well my nephews ssi & medicare were taken away from him due to receiving social security after my brother-in-laws death. my sister was told that he (my nephew) should receive his benefits when he turned 16 and that's been about a month ago. does my sister have to call the offices of his benefits or what. he really needs a new wheel chair and medication. my sister cant afford to get them on her own with out the help of his kind. this is little issue is here in texas