Indeed, there were only two legendary creatures in this world that didn't need to find an heir to replace them– it was the phoenix and the dragon.
Unlike other legendary beings that had to cultivate an heir from the start…
Phoenix and dragon usually had cubs and one of their cubs would be the one becoming the new legendary beast in the future.
Strangely, there wouldn't be only one legendary phoenix or dragon in this world, because there could be a variety of them.
For example, a legendary ice phoenix, an ice dragon, golden dragon, golden Phoenix, white dragon, white phoenix, and so on.
The dragons had more legendary dragon varieties compared to phoenix who usually only had one or two variations.
Other legendary beasts such as unicorns, griffins, pegasus, and so on, could have cubs or children, but their children would never become a legendary beast.