Hey J.,
My middle daughter did not walk until after 2 years old. Or right about that time. She also didn't talk much until closer to 3.
She has an older sister so she bascially did everything for her. being yours is an only child...I know that it is not the case. BUT maybe grown ups are doing too much for him & not forcing him to walk. Only children get spoiled that way.
My grandma watched all my girls & tended to carry them too much. My Aunt bought a walker put the kiddos in it & told my grandma NOT to pick them up any more. Leave them in the walker. So I know first hand about the grown ups doing too much first hand.
My Mom had my middle one for 1 week without me or her sister & by the time we got there...she was walking. My Mom just told her...I will NOT carry you...you will walk. Within that week...she was doing it all alone.
Just some ideas. Best of luck.