An immortal being has the ability to share their power with one soul and make them immortal too, so they can have a companion for all the years if they choose. Only one though. This being has had countless lovers and friends, and they have seen them all fade away as time passes. The being tells one of their lovers, whom they’ve been with for ten years or so, about their ability, and the lover begs to have the energy shared with them so they can be together for eternity.
"I can’t," the immortal says.
"Why not?" the lover asks.
"I’m already sharing my power."
The immortal looks down. “My cat.”