Αυτό που σου είπα γι 'αυτόν, ισχύει και για τον αδελφό του.

English Translation

What I told you about him also applies to his brother.

Ισχύει - to be valid, to be in effect…

To remember this verb try the sentence “We’re going skiing, right?” (We’re going skiing, is this valid/true/in effect?) and a translation of this is: “Θα κάνουμε σκι, ισχύει;"