  ROXs 12 (2MASS J16262803-2526477) is a young star hosting a directly imaged
companion near the deuterium-burning limit. We present a suite of
spectroscopic, imaging, and time-series observations to characterize the
physical and environmental properties of this system. Moderate-resolution
near-infrared spectroscopy of ROXs 12 B from Gemini-North/NIFS and Keck/OSIRIS
reveals signatures of low surface gravity including weak alkali absorption
lines and a triangular $H$-band pseudo-continuum shape. No signs of Pa$\beta$
emission are evident. As a population, however, we find that about half (46
$\pm$ 14\%) of young ($\lesssim$15 Myr) companions with masses $\lesssim$20
$M_\mathrm{Jup}$ possess actively accreting subdisks detected via Pa$\beta$
line emission, which represents a lower limit on the prevalence of
circumplanetary disks in general as some are expected to be in a quiescent
phase of accretion. The bolometric luminosity of the companion and age of the
host star (6$^{+4}_{-2}$ Myr) imply a mass of 17.5 $\pm$ 1.5 $M_\mathrm{Jup}$
for ROXs 12 B based on hot-start evolutionary models. We identify a wide (5100
AU) tertiary companion to this system, 2MASS J16262774-2527247, which is
heavily accreting and exhibits stochastic variability in its $K2$ light curve.
By combining $v$sin$i_*$ measurements with rotation periods from $K2$, we
constrain the line-of-sight inclinations of ROXs 12 A and 2MASS
J16262774-2527247 and find that they are misaligned by
60$^{+7}_{-11}$$^{\circ}$. In addition, the orbital axis of ROXs 12 B is likely
misaligned from the spin axis of its host star ROXs 12 A, suggesting that ROXs
12 B formed akin to fragmenting binary stars or in an equatorial disk that was
torqued by the wide stellar tertiary.
