Y4S3(Si2O7) and its solid solutions (Y1-xREx)4S3Si2O7 (RE = Eu x = 0.010–0.085, RE=Tb x = 0.010–0.500) were quantitatively prepared by reaction of starting compounds in molten CsCl. Single crystal X-Ray analysis revealed the difference in preference Eu3+ occupancy for two independent RE-sites coming from volume difference of these sites. This effect is negligible for the Tb-containing solid solution due to smaller difference in radii Tb3+ and Y3+ ions. Tb3+-containing samples are luminescent with typical emission of Tb3+, while Eu3+-containing samples are not luminescent. The 1%Tb3+-containing sample emits in blue or in green color depending on the excitation wavelength. Measured melting points are 1545 ± 15 °С for all investigated samples (Y1-xREx)4S3Si2O7.