Just a small example to drop some light on how the cases work:
показать тебя (ACCUSATIVE) to someone = to show you to someone:
Я покажу тебя моим родителям. = I will show you to my parents. I will introduce you to my parents.
показать тебе (DATIVE) something (or someone) = to show something (or someone) to you.
Я покажу тебе моих родителей. = I will show you my parents.
Please note that the word order can vary, it is not important to understand the phrase.
Я покажу тебя моим родителям. = Я покажу моим родителям тебя. - Тебя is a direct object, and моим родителям is an indirect object, regardless of the word order.
Я покажу тебе моих родителей. = Я покажу моих родителей тебе. - Тебе is an indirect object, and моих родителей is a direct object, regardless of the word order.
