  We present Keck/NIRC2 and OSIRIS near-infrared imaging and spectroscopy of
2M0441+2301 AabBab, a young (1--3 Myr) hierarchical quadruple system comprising
a low-mass star, two brown dwarfs, and a planetary-mass companion in Taurus.
All four components show spectroscopic signs of low surface gravity, and both
2M0441+2301 Aa and Ab possess Pa$\beta$ emission indicating they each harbor
accretion subdisks. Astrometry spanning 2008--2014 reveals orbital motion in
both the Aab (0.23" separation) and Bab (0.095" separation) pairs, although the
implied orbital periods of $>$300 years means dynamical masses will not be
possible in the near future. The faintest component (2M0441+2301 Bb) has an
angular $H$-band shape, strong molecular absorption (VO, CO, H$_2$O, and FeH),
and shallow alkali lines, confirming its young age, late spectral type (L1
$\pm$ 1), and low temperature ($\approx$1800~K). With individual masses of
200$^{+100}_{-50}$ Mjup, 35 $\pm$ 5 Mjup, 19 $\pm$ 3 Mjup, and 9.8 $\pm$ 1.8
Mjup, 2M0441+2301 AabBab is the lowest-mass quadruple system known. Its
hierarchical orbital architecture and mass ratios imply that it formed from the
collapse and fragmentation of a molecular cloud core, demonstrating that
planetary-mass companions can originate from a stellar-like pathway analogous
to higher-mass quadruple star systems as first speculated by Todorov et al.
More generally, cloud fragmentation may be an important formation pathway for
the massive exoplanets that are now regularly being imaged on wide orbits.

Earth and Planetary Astrophysics