We consider generalizations of the BC-type relativistic Calogero-Moser-Sutherland models, comprising of the rational, trigonometric, hyperbolic, and elliptic cases, due to Koornwinder and van Diejen, and construct an explicit eigenfunction for these generalizations. In special cases, we find the various kernel function identities, and also a Chalykh-Feigin-Sergeev-Veselov type deformation of these operators and their corresponding kernel functions, which generalize the known kernel functions for the Koornwinder-van Diejen models.Then it is a straightforward check to see that φ(x; m, −m) in (13) satisfies both difference equations.When (m J , m K ) = (m, +1/λm) for m ∈ Λ, then (27a) and (27b), using (29), becomesimplifies the four cases and allows us to find the common solution φ(x; m, +1/λm) in (13).When (m J , m K ) = (m, −1/λm) for m ∈ λ, then (27a) and (27b), using (29), becomerespectively. Choosing (34) a(m) − a(−1/λm) = −iλmβ/2 − iβ/2m (∀m ∈ Λ) reduces the equations to δ=± φ(X J + δX K ∓ iβ/2m; m, −1/λm)φ(−X J + δX K ± iβ/2m; m, −1/λm) φ(X J + δX K ± iβ/2m; m, −1/λm)φ(−X J + δX K ∓ iβ/2m; m, −1/λm) = δ=± s(X J + δX K ± iλmβ/2)s(X J + δX K ∓ iλmβ/2 ± iβ/m) s(X J + δX K ∓ iλmβ/2)s(X J + δX K ± iλmβ/2 ∓ iβ/m) 1 2 and δ=± φ(X J + δX K ± iλmβ/2; m, −1/λm)φ(−X J + δX K ∓ iλmβ/2; m, −1/λm) φ(X J + δX K ∓ iλmβ/2; m, −1/λm)φ(−X J + δX K ± iλmβ/2) = δ=± s(X J + δX K ∓ iβ/2m)s(X J + δX K ± iβ/2m ∓ iλmβ) s(X J + δX K ± iβ/2m)s(X J + δX K ∓ iβ/2m ± iλmβ) 1 2 ψ(X J − εiβ/m J ; m J ) ψ(X J ; m J ) · δ=± N K =J