Without more info or pics, I think Atzau is probably right. My guess is that, if they're window grown, they're reaching for light. Turning their pot regularly to change the direction of the light on them should get them to growing straighter.
They are leaning toward the light source just like any other plants grown by the window.
All my orchids are leaning.
I really don't like the way they look, so I constantly turn the pots, but I do not always keep at it, so some are straight and some are wavy. lol