How did my cousin find me on instagram ?

[Sian]

I have alot of pics and followers on instagram my profile was public but my username is not my real name and i havent connected it with facebook..
this morning my cousin started following me,i wonder how he found me like wtf this is so weird i dont want my relatives to know about my instagram
my cousin is so uncool i know he is now talking shit about me saying she has too many pics and has many followers
how do i keep my instagram safe and not let my relatives find me ?
how did he find me when i have not connected it to facebook and my username is not my real name ?

[asia]

Maybe trough your friends that are following you,or maybe seen when you are logged in,or maybe have similar username on some other website she knows about,or maybe trough your email address

[Rayan]

Maybe you registered your number on your profile and your cousin have your phone. He might found you by phonebook lookup.

[Jim]

He found you because you violated the #1 rule of the internet: If you don't want the whole world to see something, don't post it on the WORLD-WIDE web!