splitting the video feed
Assuming the video signal is analog, you need some form of amplifier to feed multiple LCD screens UNLESS the LCD unit has looping inputs, which most vehicular ones don't. While I don't know of a handy aftermarket 12 volt video distribution amplifier, I'll bet one of the aftermarket companies has something along those lines. Regardless of looping or not, I'd use a distribution amp to isolate one display from the next.
In the 2011 & 2012 X3's and other BMW's, a lot of the video and data is on a fiber-optic network called the MOST bus. As I am very new to the 2012, I don't know what species the connection is.