Normally there is only one Hummingbird at our feeder at a time. This is because it is guarded by a female somewhere high in the trees. If she sees another Hummingbird there, she dives in and sends it away unceremoniously. When she is feeding, any Hummingbird that comes by is given chase.
Early this morning a different scene took place. She was feeding calmly when a younger Hummingbird approached. She lifted her head and looked at it but did not start any threatening move. I think that was her daughter, and she allowed her to share the feeder.
After that the mother flew away peacefully. The daughter went around the feeder a few times.