no puberty in a 18 years old boy. Also, I lack a sense of smell

Hey guys im almost 18 years old but i have no signs ppof puberty im 5.5 feet with really narrow shoulders and my testicles and penis are like a kid i have no facial or armpit hair at all just 4 5 pubic hairs my voice also is like 12 years old i first had 2 3 pubic hairs when i was 15 but since then i haven't grown an inch my brother who is 16 has hit puberty a year ago he has facial hair and deep voice Also i lack sense of smell