We report on VLT/GIRAFFE spectra of stars in two recently discovered ultra-faint satellites, Reticulum 2 andHorologium 1, obtained as part of theGaia-ESO Survey. We identify 18 members in Reticulum 2 andfive inHorologium 1. Wefind Reticulum 2 to have a velocity dispersion of3.22km s0.491.641-+-, implying a mass-to-lightratio(M/L)of∼500. The mean metallicity of Reticulum 2 isFe H2.46=-, with an intrinsic dispersion of∼0.3 dex andα-enhancement of∼0.4 dex. We conclude that Reticulum 2 is a dwarf galaxy. We also report on theserendipitous discovery of four stars in a previously unknown stellar substructure near Reticulum 2 withFe H2~-andV220 km shel1~-, far from the systemic velocity of Reticulum 2. For Horologium 1 we infer avelocity dispersion ofV4.9 km s0.92.81()s=-+-and aM/Lratio of∼600, leading us to conclude that Horologium 1 isalso a dwarf galaxy. Horologium 1 is slightly more metal-poor than Reticulum 2(Fe H2.76=-)and issimilarlyα-enhanced:Fe 0.3 dexa~with a significant spread of metallicities of 0.17 dex. The line-of-sightvelocity of Reticulum 2 is offset by 100 km s−1from the prediction of the orbital velocity of the Large MagellanicCloud(LMC), thus making its association with the Cloud uncertain. However, at the location of Horologium 1,both the backward-integrated orbit of the LMC and its halo are predicted to have radial velocities similar to that ofthe dwarf. Therefore, it is possible that Horologium 1 is or once was a member of the Magellanic family.