It's not generally a good idea to split a microphone signal simply by using "Y"-cables, because then each microphone has to drive two inputs, and the load (burden) on the microphone is doubled; it has to produce twice as much signal current.
(Another way of saying the same thing: The two inputs are in parallel, thus their combined impedance is roughly half what each one's impedance would be separately.)
Whether the phantom powering from one input might damage the other one, and/or whether the presence of the second input would pull the phantom powering out of spec and make the microphones not work (or not work well), depends entirely on the circuit design of the two inputs. Again, not a risk worth taking IMO.
On the other hand, if you are strongly motivated--there are "mic splitters" (with transformers inside) that do this kind of thing without introducing these risks. But if you decide to use them, test the whole setup before the recording; depending on the splitters you use, the phantom powering may require special attention (e.g. many splitters will pass phantom powering through only one of their outputs, while blocking it on the other one or ones, so you need to make sure to power the one output of the splitter that will pass the powering along to the microphone).
--best regards
(Edited later to add:) Mike splitters can be OK, but what I would rather do in this situation is connect the mikes to a preamp, and split the outputs of the preamp. Fewer issues that way ...