For all satellite galaxies at z = 0 with ﹩{M}_{\mathrm{star}}={10}^{3-9}\;\;{M}_{\odot }﹩ that experienced a major merger with another satellite after falling into the MW/M31 halo, the fraction of such mergers that fell in as part of the same host halo (group), as a function of the time since (or redshift of) the last major merger, ﹩{T}_{\mathrm{LMM}}﹩ (or ﹩{z}_{\mathrm{LMM}}﹩). We do not find any significant dependence on satellite mass. Infalling groups drive the majority (60%–90%) of all satellite–satellite mergers.