two or more photons can occupy the same space.
two or more quarks cannot.
the three quarks in a hadron do not merge into one large quark. the strong force does not explain this, neither does electromagnetism, or gravity, or the weak force, or the higgs mechanism.
physicists will brush this off "oh it's caused by the pauli exclusion principle" which is about as useful as saying that babies are caused by pregnancy.
none of the known forces explain why quarks behave in this way!