We explore multiple-cation chalco-halide phase fields evaluated by their synthetic accessibility using machine learning models. Exploratory synthesis guided by computational tools leads to the discovery of two new compounds; CuSn2SI3 and Cu0.35Sn5.29S2I7, their structures, and electronic and optical properties are reported herein. This is the first report of a stable quaternary compound in the Cu-Sn-S-I phase field. The two new compounds show related crystal structures where Sn4S2I4 layers are a common structural motif in both. These Sn4S2I4 layers are connected by Cu2I2 layers and disordered Cu-Sn-I layers, forming the three-dimensional structures of CuSn2SI3 and Cu0.35Sn5.29S2I7 respectively. Electronic band structure calculations using density functional theory show the presence of a direct band gap in CuSn2SI3 and suggest anisotropic transport, in line with the layered structure of the compound. A mixture of the two compounds with ~86% CuSn2SI3, shows a band gap in the visible region, close to 2.1 eV and a significant photo-induced charge carrier mobility of ~1.3 cm2/V s. This demonstrates Cu-Sn chalco-halides can form a promising phase space to explore for solar absorber materials, with further design and tuning of band gap.