No rule for this one
No ending or word group predicts the article of Onkel. Learn it as a pair and say it out loud: der Onkel.
der Onkel
It's der Onkel. Onkel is masculine, plural die Onkel.
Mein Onkel wohnt in Islamabad.
My uncle lives in Islamabad.
No ending or word group predicts the article of Onkel. Learn it as a pair and say it out loud: der Onkel.