We find a two-parameter family of coupled Painlev\'e systems in dimension four with affine Weyl group symmetry of type $A_4^{ (2)}$. For a degenerate system of $A_4^{ (2)}$ system, we also find a one-parameter family of coupled Painlev\'e systems in dimension four with affine Weyl group symmetry of type $A_1^{ (1)}$. We show that for each system, we give its symmetry and holomorphy conditions. These symmetries, holomorphy conditions and invariant divisors are new. Moreover, we find a one-parameter family of partial differential systems in three variables with $W(A_1^{ (1)})$-symmetry. We show the relation between its polynomial Hamiltonian system and an autonomous version of the system of type $A_1^{ (1)}$.
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