Milestone: A significant event or stage in the life, progress, development, or the like of a person.
We all have milestones in our lives. For instance, when your children are born. Then they have children and you become a grandparent. That is a wonderful milestone. I first experienced it in 1989 when my first grandchild, Chelsea, was born.
And now Chelsea has a beautiful little daughter. Believe me, being a great-grandparent is a milestone!
Gabby, welcome to the world.