Earthchild

It was called the Mouat-Gari process. It gave to all of Earth's children man's oldest dream---immortality. For Kurt Kraus, torn from his family, attacked and persecuted by a generation he was destined to see age and die before his eyes, the first years of eternal life were the hardest.

But as a century passed, and Kurt found himself one of Earth's ageless rulers, he discovered immortality's terrible price, and the awful choice mankind had to make to redeem its future.

This is #1 in The Earth Song Triad.