If two particles with the same mass are made of photons, they must be made of the same amount of photons.
This would make the 2 particles have identical properties, and we already know that we can have particles with different properties and the same mass.
Therefore the particles cannot be made of photons.
mass = relativistic mass
Ok, entry 3, steve100.
An example of what steve100 is talking about is an electron and a positron. Is this correct?