We have determined the scattering angle dependence of the complex amplitudes for populating the magnetic substates of the doubly excited states (1s2121') (2)L of C3+ and B2+ following double electron capture at low energies. This is achieved by measuring the three-dimensional Auger anisotropy through detection of the energy-analyzed Auger electron in coincidence with the scattered projectile. These measurements represent the most detailed study of double electron transfer. One of the most striking results is the tendency for the angular momentum transferred to the projectile to reach its maximum value, i.e. \L\ = 1, 2 for P-2, D-2 states respectively as has been observed for excitation and single capture processes.