  We use 20 years of astrometric data from the RECONS program on the
CTIO/SMARTS 0.9-m to provide new insight into multiple star systems in the
solar neighborhood. We provide new and updated parallaxes for 210 systems and
derive nine high-quality astrometric orbits with periods of 2.49 - 16.63 years.
Using a total of 542 systems' parallaxes from RECONS, we compare systems within
25 parsecs to Gaia DR2 to define criteria for selecting unresolved astrometric
multiples from the DR2 results. We find that three out of four unresolved
multi-star red dwarf systems within 25 pc in DR2 have parallax_error $\geq
0.32$ mas, astrometric_gof_al $\geq 56$, astrometric_excess_noise_sig $\geq
108.0$, ruwe $\geq 2.0$, and parallaxes more than $\sim$10% different than the
long-term RECONS results. These criteria have broad applications to any work
targeting nearby stars, from studies seeking binary systems to efforts
targeting single stars for planet searches.
