The values of the Landé g factors of the i³∏ _g^-, v, N and j³Δ_g^- v, N states of the H₂, HD, and D₂ molecules have been found semiempirically for the following vibrational and rotational quantum numbers: v≤ 3; N ≤ 7 for H₂; N ≤ 5 for HD; and N ≤ 11 for D₂. These values were obtained in terms of the nonadiabatic model, which takes into account the interaction between the 3dπ ³∏_g and 3dδ³Δ_g states with the same values of v and N in the approximation of pure precession, with the use of semiempirical values of the expansion coefficients of the wave functions in the Born-Oppenheimer basis determined by us previously and the results of numerical calculation of the overlap integrals of the vibrational wave functions of these states. The results obtained for the H₂ molecule are in good agreement with the data in the literature. For the i ³∏_g^- and j³Δ _g^- states of the HD and D₂ molecules, the g factors were found for the first time. This made it possible to study for the first time the role of the isotopic effect in the perturbation of the dependences of the g factors of rovibrational levels on v and N for the triplet electronic states of the hydrogen molecule. It was found that the interference effects of interaction between the 3dπ³∏_g and 3dδ³Δ_g states lead both to significant differences - up to 8, 6, and 11 times for H₂, HD, and D ₂, respectively (the i³∏_g^- state), 20 times for H₂ and HD, and two orders of magnitude for D₂ (the j³Δ_g^- state) - between the nonadiabatic values of the g factors and the corresponding adiabatic values for some isotopomers of the hydrogen molecule and to significant differences - up to 9 and 1.5 times for the j ³Δ_g^- and i³∏ _g^- states, respectively - in the nonadiabatic values of the g factors of rovibrational levels of different isotopomers of the hydrogen molecule.