I wonder how it could remove my iCloud account? helppppp

ipod touch 5 ios 8.3 I wonder how it could remove my iCloud account , because to me two years ago I was given a ipod touch 5, and a year ago I got an iPhone 5 and iPod is what gave my mother but my sister is very involved and I believe him icloud account with an email hacked him to my mother as I do to remove it ??????