We start with a Riemann-Hilbert problem (RHP) related to a BD.I-type symmetric spaces SO(2r + 1)/S(O(2r − 2s + 1) ⊗ O(2s)), s ≥ 1. We consider two Riemann-Hilbert problems: the first formulated on the real axis R in the complex λ-plane; the second one is formulated on R ⊕ iR. The first RHP for s = 1 allows one to solve the Kulish-Sklyanin (KS) model; the second RHP is relevant for a new type of KS model. An important example for nontrivial deep reductions of KS model is given. Its effect on the scattering matrix is formulated. In particular we obtain new 2-component NLS equations. Finally, using the Wronskian relations we demonstrate that the inverse scattering method for KS models may be understood as a generalized Fourier transforms. Thus we have a tool to derive all their fundamental properties, including the hierarchy of equations and he hierarchy of their Hamiltonian structures.Important tools for reducing the ISP to a Riemann-Hilbert problem (RHP) are the fundamental analytic solution (FAS) χ ± (x, t, λ). Their construction is based on the generalized Gauss decomposition of T (λ, t)Here S ± J and T ± J are upper-and lower-block-triangular matrices, while D ± J (λ) are block-diagonal matrices with the same block structure as T (λ, t) above. Skipping the details we give the explicit expressions of the Gauss factors in terms of the matrix elements of T (λ, t) S ± J (t, λ) = exp