No, this isn't what the Bible teaches. The Bible tells us there will be a vast number of people in heaven -- so many that no one could count them (see Revelation 7:9).
The Bible tells us many truths about heaven -- but the most important is that heaven is the place where God is. In other words, in heaven we will be in God's presence forever. Think of it! And not only will we be with God, but we will be with Jesus, who came to take us to heaven forever. His promise is for all who put their faith and trust in Him for their salvation: "In my Father's house are many rooms.... I am going there to prepare a place for you. And if I go and prepare a place for you, I will come back and take you to be with me" (John 14:2-3).
Don't be misled by those who twist what the Bible says or turn their back on its clear meaning. Jesus Christ came for one reason: to make it possible for us to go to heaven when we die. He did this by taking all our sins upon Himself and dying on the cross for us. Now He offers us the gift of eternal life.
Have you accepted that gift? You can, by confessing your sins to God and asking Christ to come into your life as your Lord and Savior. And pray for your cousin, that he too may put his faith in Christ.