Anyone familiar with Dyselxia?

My father had dyslexia as a child. I always thought that was a lifelong thing but he said he got alot of special education and training and fixed it because now, as an adult, he doesn't suffer with it. Well now, we're wondering if my nephew has it. He's almost 6 years old and just started kindergarten. He can't recognize ANY of his letters. However, if you ask him what letter "i" is, he says it's an explanation point. We find it really weird how he can remember such a detailed word but can't remember the name of the letter. Supposedly, all of the kids in the cl are learning their alphabet very easily but he's having problems. He attended a good pre-school and my sister goes through the alphabet with him at home but nothing has helped. She mentioned she wonders if dyslexia might be hereditary or if he has it. Any ideas?