how to become a muscular boy???

sigh..
when everybody look at me or see me..they will say:''Aiyo she zhe,why you are so thin?Arent your parents feed you?''When i heard this,it really makes my heart get hurt...
Why im so thin?I used to think it before and i have done some research.
According to my research,the most probably is cause by genetic..
my dad was a thin boy when he was young..and i think this is the main fact that cause me cant grow fatter..but many years later,my dad becomes better,at least his muscle is bigger than me..haha
therefore, i have decided to 'make up' my body...at least maintain a nice shape of body..
with a wider shoulder,i can wear whatever shirt that i like because it will looks better..
wakakka..
i want someone to give me some opinion...
please...