The quaternary KxSn6-2xBi2+xSe9 and KSn5Bi5Se13 were discovered from reactions involving K2Se, Bi2Se3, Sn, and Se. The single crystal structures reveal that KxSn(6-2x)Bi(2+x)Se(9) is isostructural to the mineral heyrovskyite, Pb6Bi2S9, crystallizing in the space group Cmcm with a = 4.2096(4) Angstrom, b = 14.006(l) Angstrom, and c = 32.451(3) Angstrom while KSn5-Bi5Se13 adopts a novel monoclinic structure type (C2/m, a = 13.879(4) Angstrom, b = 4.205(l) Angstrom, c = 23.363(6) Angstrom, beta = 99.012(4)degrees). These compounds formally belong to the lillianite homologous series xPbS.Bi2S3, whose characteristic is derivation of the structure by tropochemical cell-twinning on the (311) plane of the NaCl-type lattice with a mirror as twin operation. The structures of KxSn6-2xBi2+xSe9 and KSn5Bi5Se13 differ in the width of the NaCl-type slabs that form the three-dimensional arrangement. While cell-twinning of 7 octahedra wide slabs results in the heyrovskyite structure, 4 and 5 octahedra wide slabs alternate in the structure of KSn5Bi5Se13, In both structures, the Bi and Sn atoms are extensively disordered over the metal sites. Some physicochemical properties of KxSn6-2xBi2+xSe9 and KSn5Bi5Se13 are reported.