Two rf 433 transmiter and one receiver connection won't work?
The transmitters don't transmit at exactly the same frequency - there may be tens of kHz difference - the receiver however is matched to the transmitter and, from what I know and have read about these particular devices, there is a manual adjuster on the receiver to bring it into near-perfect alignment with the transmitter it is paired with.



Notice the screw terminal on the receiver - this is, I believe, an adjuster that can align the receiver's operating frequency with the transmitter. Basically this means that two randomly chosen transmitters are unlikely to be at the same frequency and, as a result, one setting of the screw on the receiver will not suit both transmitters.

They are $5 a pair so you get what you pay for.