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We present the first results from our Keck program investigating the orbitalarchitectures of planet-hosting multiple star systems. Kepler-444 is ametal-poor triple star system that hosts five sub-Earth-sized planets orbitingthe primary star (Kepler-444A), as well as a spatially unresolved pair of Mdwarfs (Kepler-444BC) at a projected distance of 1.8" (66 AU). We combine ourKeck/NIRC2 adaptive optics astrometry with multi-epoch Keck/HIRES RVs of allthree stars to determine a precise orbit for the BC pair around A, given theirempirically constrained masses. We measure minimal astrometric motion($1.0\pm0.6$ mas yr$^{-1}$, or $0.17\pm0.10$ km s$^{-1}$), but our RVs revealsignificant orbital velocity ($1.7\pm0.2$ km s$^{-1}$) and acceleration($7.8\pm0.5$ m s$^{-1}$ yr$^{-1}$). We determine a highly eccentric stellarorbit ($e=0.864\pm0.023$) that brings the tight M dwarf pair within$5.0^{+0.9}_{-1.0}$ AU of the planetary system. We validate that the system isdynamically stable in its present configuration via n-body simulations. We findthat the A$-$BC orbit and planetary orbits are likely aligned (98%) given thatthey both have edge-on orbits and misalignment induces precession of theplanets out of transit. We conclude that the stars were likely on their currentorbits during the epoch of planet formation, truncating the protoplanetary diskat $\approx$2 AU. This truncated disk would have been severely depleted ofsolid material from which to form the total $\approx$1.5 $M_{\rm Earth}$ ofplanets. We thereby strongly constrain the efficiency of the conversion of dustinto planets and suggest that the Kepler-444 system is consistent with modelsthat explain the formation of more typical close-in Kepler planets in normal,not truncated, disks.

Orbital Architectures of Planet-Hosting Binaries: I. Forming Five Small Planets in the Truncated Disk of Kepler-444A