  If binary black holes form following the successive core collapses of
sufficiently massive binary stars, precessional dynamics may align their spins
$\mathbf S_1$ and $\mathbf S_2$ and the orbital angular momentum $\mathbf L$
into a plane in which they jointly precess about the total angular momentum
$\mathbf J$. These spin orientations are known as spin-orbit resonances since
$\mathbf S_1$, $\mathbf S_2$, and $\mathbf L$ all precess at the same frequency
to maintain their planar configuration. Two families of such spin-orbit
resonances exist, alike in dignity but differentiated by whether the components
of the two spins in the orbital plane are either aligned or antialigned. The
fraction of binary black holes in each family is determined by the stellar
evolution of their progenitors, so if gravitational-wave detectors could
measure this fraction they could provide important insights into astrophysical
formation scenarios for binary black holes. In this paper, we show that even
under the conservative assumption that binary black holes are observed along
the direction of $\mathbf J$ (where precession-induced modulations to the
gravitational waveforms are minimized), the waveforms of many members of each
resonant family can be distinguished from all members of the opposing family in
events with signal-to-noise ratios $\rho \simeq 10$, typical of those expected
for the first detections with Advanced LIGO/Virgo. We hope that our preliminary
findings inspire a greater appreciation of the capability of gravitational-wave
detectors to constrain stellar astrophysics and stimulate further studies of
the distinguishability of spin-orbit resonant families in more expanded regions
of binary black-hole parameter space.
