We present a neutron powder-diffraction study of the monoclinic double perovskite systems Nd2NaB′O6 (B′=Ru, Os), with magnetic atoms occupying both the A and B′ sites of the A2BB′O6 structure. Our measurements reveal coupled spin ordering between the Nd and B′ atoms with magnetic transition temperatures of 14.3(1) K for Nd2NaRuO6 and 16.2(2) K for Nd2NaOsO6. There is a type-I antiferromagnetic structure associated with the Ru and Os sublattices, with the ferromagnetic planes stacked along the c axis and [110] direction respectively, while the Nd sublattices exhibit complex, canted antiferromagnetism with different spin arrangements in each system.