First, you may want to UNparent the Floor from the Ceiling.
Select the Floor and using the pull down menu, Change parent to "Universe."

You want ONE parent (either the floor or the seiling)
Per your graphic, you have the Floor parented to the ceiling.
If you want the ceiling to be the parent (i.e., like the "hip" in a human figure) ...
Then click (on the symbol) for each of the other parts and drag them to the "ceiling so that all objects are parented to the ceiling.
Now, click on (select)  the ceiling and then click on the "Create New Figure" button.
Walla !

cheers,
dr geep
;=]

Remember ... "With Poser, all things are possible, and poseable!"

cheers,

dr geep ... :o]

edited 10/5/2019