Nuoc Nut was discovered in 2003, long before nearby Hang Va. A connection between the two was discovered in 2016. There seems to be no physical connection with Son Doong, though they probably share the same underground waterflow. Nuoc Nut is 2.2km long and is probably about 2 million years old.
Please see pictures of Hang Nước Nứt:
Source: Oxalisadventure.com