if he is a BC or BC mix then I would fully expect the weight you describe. one of my BCs, Happy, she is 6 years old and you can feel her spine, hip bones and ribs..and she is on the porky side for her lol Misty, my other BC did not fill out till she was 3 years old, before that she was incredably scrawny, people would tell me that she looked like she would snap in half lol, yet she was NOT underweight, she was infact a very healthy weight.