Parent halo mass as a function of total stellar mass at z ~ 3.3 from the Illustris simulation (Vogelsberger et al. 2014) for nearly equal mass M₁/M₂ < 10 galaxy pairs with a separation smaller than 50 kpc. The position of our dual AGN pair system is indicated by the vertical black line, with uncertainties highlighted by the red shaded area. There is no similar system in Illustris due to the limited volume (106.5 Mpc³ comoving), but the extrapolation from lower masses (dashed line) implies a parent halo mass of 12.8 < log(M_halo/M_⊙) < 13.7.