You can treat such networks with the usual Kirchoff's kind of analysis, but you can't just multiply the transfer functions to get the total transfer function. You would get an extra voltage drop at the output of the first network that would need to be taken into account. (This could be fixed by placing an active buffer between the sections; this would provide extra current to the second section, so that the voltage at the output of the first is maintained, regardless of the second section's impedance.)