Learn Texas Holdem

Question: Me and my uncle were playing Texas hold'em, and a tie occurred. there was two pairs on the board, three's and 8's. I bet a rather large sum, and my uncle called it. When we turned over our hands, we both had aces to make two pairs, aces high. However, he had a king as the next highest card, and I had a 10. He said that he wins the pot, because his 6th card was the highest. I said that the 6th card was irrelevant, and that we should split the pot. Who is correct in this situation?