When my father tries to run xsane it says that there is no device found. I have followed all steps outlined in this web page for the Brother 240C scanner. Here is the link: http://solutions.brother.com/linux/sol/printer/linux/sane_drivers.html. I also wrote my own rules file under /etc/udev/61-brother.rules.
As sane-backends doesn't contain the driver for that particular piece of hardware, it needn't contain the udev rules -- they should be shipped with the driver itself.