Only God knows your uncle's heart, of course, and whether or not he truly repented of his sins on his deathbed and trusted Christ as his Lord and Savior.
But it sounds as if he did–and if so, you should rejoice! Jesus said that "there is rejoicing in the presence of the angels of God over one sinner who repents" (Luke 15:10). If the angels rejoice over the salvation of someone who repents (no matter how bad they were), then so should we. The alternative for them was an eternity separated from God in the place the Bible calls Hell–and that should cause us great sadness. Remember, "Christ Jesus came into the world to save sinners" (1 Timothy 1:15).
It's natural to wonder if it's fair for God to save someone at the last minute when others have served Him all their lives; people asked Jesus the same question (see Matthew 20:1-16). But remember: None of us deserves salvation; no matter how good we are, we are saved solely by God's grace through faith in Christ.
In addition, never forget what it cost your uncle to wait until the last minute to come to Christ. It cost him the joy of knowing Christ's presence and guidance every day. Be sure of your own commitment to Christ–and then be grateful for His love and mercy, both for you and for your uncle.