You can cut the root off any side plants off the parent plant..the biggest plant...try to get some root and leaves of the sprout . I do this in the spring or after the flowering in August.
You should do two or more suckers off the main root....and when moving dig deep enough hole for all of the root...some may take, some do not....but I have sooo many off shoots I can keep trying 10 times or more. I live in Wisconsin and my Yuccas love my well drained soil with rocks for on top for good drainage
I have no idea how or why they bloom..sometimes just one..this year 7 of them bloomed...anynhelp on that...or is it just the luck of the plant and the weather!