Yes and No – in other words, it depends.
The cellphone switching system will not service two phones that identify themselves identically. The communications protocols assume that the subscriber number is a unique identifier, and things go badly wrong if the system keeps thinking the same device is in two different places simultaneously.
On the other hand, you can get a telephone number from a VoIP service provider and configure it so that it rings two different mobile phones simultaneously and had the call off to the first one that answers. You can also run a VoIP telephone application on those same telephones that routes outgoing calls through the VoIP switch and presents that VoIP telephone number as the originating number in the Caller-ID data.