Often yes, but only when the divider is reciprocal, the manufacturer permits reverse use, and the input signals meet the required amplitude, phase and power conditions. A 0-degree divider used in reverse produces the vector sum at the common port; it does not simply add two headline power ratings.
Equal coherent inputs that are in phase combine efficiently. Phase or amplitude error reduces wanted output and can send power into the isolation resistor or another source path. Uncorrelated signals, a missing source, a reflected load or an unlocked phase relationship therefore create different internal dissipation and fault stress.
For an RFQ, state frequency, signal coherence, relative phase and amplitude tolerance, average and peak power per input, output VSWR, fault duration and allowable source-to-source coupling. Confirm both the matched power rating and the isolation-resistor or internal-load dissipation rating before acceptance testing.