Structural and magnetic properties of (Nd1-xRx)3Fe27.31Ti1.69 compounds with R = Dy or Er have been investigated by means of x-ray diffraction and magnetic measurements. All compounds with x ≤ 0.5 for R = Er or with x ≤ 0.6 for R = Dy crystallize in Nd3(Fe, Ti)29-type structure. Substitution of Er or Dy for Nd leads to a contraction of unit-cell volume. The Curie temperature TC of (Nd1-xDyx)3Fe27.31Ti1.69 compounds increases almost linearly with increasing Dy content, whereas TC of the (Nd1-xErx)3Fe27.31Ti1.69 compounds decreases monotonically with increasing Er content. Saturation moments Ms of the (Nd1-xRx)3Fe27.31Ti1.69 compounds decrease with increasing x for both R = Er and Dy. As temperature lowers from room temperature to 5 K, a spin reorientation from the easy plane to the easy cone occurs for (Nd1-xErx)3Fe27.31Ti1.69 and two spin reorientations from the easy plane to two different easy cones occur for the (Nd1-xDyx)3Fe27.31Ti1.69 compounds. The anisotropy field Ba at room temperature for (Nd1-xDyx)3Fe27.31Ti1.69 compounds increases with increasing Dy content, whereas Ba for (Nd1-xErx)3Fe27.31Ti1.69 compounds decreases with increasing Er content. Spin phase diagrams have been constructed for both (Nd1-xDyx)3Fe27.31Ti1.69 and (Nd1-xErx)3Fe27.31 Ti1.69 compounds.