The nearest pre-main sequence multiple stars

Protoplanetary disks are where planets form; and where the pre-biotic materials which produce life-bearing worlds are assembled or produced. We need to understand them, how they interact with their central stars, and their evolution both to reconstruct the Solar System's history, and to account for the observed diversity of exo-planetary systems. Our knowledge of these systems, in terms of their disks, gas content, dust mineralogy, and accretion is most complete for the nearby PMS A stars, the Herbig Ae stars. Previously, many of the nearby Herbig Ae stars were thought to be single stars: a new generation of high angular resolution and high contrast imagery has revealed a number of binary, and multiple star systems, with a wide range of signatures of dynamical interaction with the primary star. Our current understanding of these systems is reviewed.