Memory can keep somebody young while time continues changing their witnesses.

Someone who is gone stops changing. They stay the age they were, wearing the same coat, speaking in the voice you last heard, while everybody who remembers them keeps moving further along. That gap can be strange to notice, especially when you reach an age they never got to. Nothing is wrong with you when it arrives; it is simply what remembering does over a long stretch of time.

If a person is held that way in you, you might say aloud how old you are now beside them. Some people find it steadying to tell a story about them to somebody who never met them.