One twin brother travels away at the speed of light for five years and then comes back to find his twin brother fifty years older while he is only ten years older.

How?

Okay, so animated educational videos probably are not
quite the thing you are looking for when you come to this site, but it is interesting.

Time dialation is a hard concept to understand, and I think these guys did a great job with explaining how it works.

I will admit that I got lost a couple times, but I got the basic concept and that is what counts.