Who is Kiri's father in 'Avatar: The Way of Water'?

We meet the biggest mystery of Avatar: The Way of Water less than five minutes into the movie. That mystery is Kiri (Sigourney Weaver), a young Na'vi child who is the daughter of scientist Grace (also Weaver) from the first Avatar.

"But wait," you may ask. "Didn't Grace die in the first movie? I don't remember her having a...