Avatar: The Last Airbender / The Legend of Korra - Image #339,236

This will come in handy in 10 years so it'll be a good low blow to this new generation's childhood.

@Philipp1987

He knew because his father had his bloodbending sealed away, yet both he and his brother were able to inherit their father's bloodbending abilities. So he knew, from his own personal experience, that the de-bended can have bender children.