Simulated and observed luminosity ratios of satellite-of-satellite systems as a function of the luminosity of the main dwarf. The gray dots correspond to the six satellite-of-satellite systems analyzed in the FIRE simulation (Wheeler et al. 2015), and the black dots show the 14 satellite-of-satellite systems identified in the zoom-in simulations of Revaz & Jablonka (2018). The colored square and triangles are measurements from observed satellite-of-satellite systems. The line indicates the resolution limit of the Illustris-TNG50 simulation.