  Asteroid families with ages younger than $1$ Myr offer an interesting
possibility of studying the outcomes of asteroid disruptions that are little
modified by subsequent evolutionary processes. We analyze a very young asteroid
family associated with (18777) Hobson in the central part of the main belt. We
aim at (i) understanding its peculiar size distribution, and (ii) setting an
upper limit on the characteristic dispersal velocity at subkilometer sizes
corresponding to the smallest visible Hobson members. We identified the Hobson
family using an up-to-date asteroid catalog. A significant increase in the
number of its known members allowed us to study their size distribution and
compare it with computer simulations of catastrophic disruptions. Backward
orbital integrations of the heliocentric orbits allowed us to confirm the
previously suggested age of Hobson and helped to estimate limits of the
ejection speed. The Hobson family has an unusual size distribution: two nearly
equal-size bodies, followed by a population of smaller asteroids, whose
distribution takes a characteristic power law. There are two possibilities to
explain these data. Either a canonical impact onto a single parent body,
requiring fine-tuned impact conditions that have not been studied so far, or an
unconventional model for the parent object of the Hobson family, namely a
binary with $\simeq 7-9$ km primary and a $\simeq 2.5$ km secondary. In the
latter case, the primary was disrupted, leaving behind the largest remnant
(18777) Hobson and a suite of subkilometer asteroids. The second largest
asteroid, (57738) 2001 UZ160, is the nearly intact satellite of the parent
binary. The excellent convergence of nominal orbits of Hobson members sets an
upper limit of $\simeq (10-20)$ m s$^{-1}$ for the initial dispersal velocity
of the known members, which is consistent with both formation models.
