What fact about the tucks are revealed PG?

In "Tuck Everlasting," it is revealed that the Tuck family has gained immortality due to drinking from a magical spring. This immortality means they do not age and cannot die from natural causes, leading to both advantages and challenges in their lives. The Tucks are deeply aware of the loneliness and isolation that come with eternal life, as they watch loved ones age and pass away while they remain unchanged. This revelation serves as a central theme of the story, exploring the implications of immortality and the value of life.