She can forgive him for not being all that good at jokes. After all, who would really want the incarnation of death getting funny with things? It's probably better this way.

Toriel does perk up at the mention of his family, though. She may have read about his family some, but it's entirely another thing to hear about them firsthand. "Do you? How wonderful! I am sure she means a lot to you."

She can only dream of being a grandmother. At least for the time being. When you're functionally immortal, it's only a matter of time.