The influence of hydrogenation on the magnetic properties of the compounds GdFe3, Gd6Fe23, DyFe3 and Dy6Fe23 has been investigated by measurements of powder high field magnetization at 4.2 K in pulsed fields up to 38 T. The magnetization curves of the hydrides GdFe3Hx and Gd6Fe23Hx show the spin-flip transition from the ferrimagnetic state to a noncollinear spin structure at the critical field Bc. The exchange coupling nRT between the R and the Fe sublattices was estimated from the slope dM/dB above Bc. The values of nRT, Bc and the compensation temperature Tcomp decrease with increasing hydrogen composition, indicating a weakening in the RT coupling. The magnetization of the hydrides DyFe3Hx and Dy6Fe23Hx does not reach saturation even at 38 T. In the Dy hydrides the magnetocrystalline anisotropy for the Dy ion competes with nRT which is weakened upon hydrogenation. The fanning effect is revealed by the Dy moments at the ground state of Dy6Fe23H12. The Fe moment increases in the initial stages of absorption of hydrogen and then decreases as more hydrogen is absorbed.