Nobody can live forever because when people are born a bit of 'forever' has already passed them by. People are not 'around' - for instance - when their parents are babies.
Eternity is an absolute and cannot be interrupted.
Infinity is also an absolute and cannot be demarcated.
Absolutes cannot be broken down and parcelled out in pieces.
Therefore if somebody says to you, 'Follow me and you will live forever,' they are lying and you would best be advised to look for ulterior motives because liars only ever serve their own best interests - not yours.