Electroplating an alloy from separate metal solutions
In short, yes, it is possible to electroplate alloys, but it isn't as simple as just mixing the ions you want in the ratio you want.
In the simplest approximation, the alloy deposition would behave as two simultaneous, separate depositions at the same voltage and the composition could be controlled by changing the voltage, assuming each component has a different current-voltage response.
In the real world, unfortunately, there are numerous interactions between the ions in solution, the metals on the electrode, etc. and the outcome becomes quite complex to predict.
Here is a decent open-access review of the chemistry and applications of this type of process.