Eternal union with God has often been portrayed by religious groups as the resurrection of the body - the whole person who lived on planet Earth.
Bible teaching is however explicit and clear. However fundamentalists systematically misinterpret it and even contradict what it plainly says. Consequently they get into silly questions like how old will the body be, how will atoms scattered across the universe be reassembled etc etc.
The Bible unambiguously denies that these bodies will ever be reassembled (1 Cor 15:37) The clearest ressurrection teaching is in 1 Cor chapter 15. (see 1 Cor 15:50) "flesh & blood cannot inherit the Kingdom of God."
When the Saducees questioned Jesus about the resurrection of the dead, he replied that God was not a God of the dead but of the living. He did not comment on where or in what state Abraham Isaac & Jacob were, but they were clearly 'alive'.
The resurrection is the foundation stone of Christian faith. The absolute uniqueness of Jesus lies not in his teaching, or his life or death, but in his resurrection.
Just my hurried comments.