Series Termination Resistors Sharing a Common Point
It really depends on the line lengths.

If the line is long between your signal generator and the two inputs, and the latter are close together you need to terminate the line with an impedance that includes both input capacitances and a single resistor. 

If the line splits and goes some distance to the two loads, you should, in reality, split the signal properly into two, propagate each, and terminate at each gate.