Yes lilies grow from bulbs, but I'm not sure about splitting them. I do
know that once a cluster of lilies gets too thick, they do grow and flower better if separated. It sounds like you have them planted fairly far apart; how long have those bulbs been in that spot?
I wouldn't be worried yet, though, if they haven't flowered - unless you were in Louisville with me.
Glad you enjoyed my pics, Fluff!