When I make an adult mobs appear with two babys and make a command like / kill or / tp there is a new weird selector pointing to the adult creature.
MC-139185
Unknown target in command
Resolved
Works As Intended
1
(Unassigned)
Unconfirmed
Minecraft 1.13.2, Minecraft 18w43b, Minecraft 18w43c, Minecraft 18w44a, Minecraft 18w45a
Retrieved
That is the UUID selector, allowing you to select just the mob you are pointing at.