Four new quaternary isostructural rare-earth thiosilicates, ZnY6Si2S14 (1), Al0.50Dy3(Si0.50Al0.50)S-7 (2)2 Al0.38Dy3-(Si0.85Al0.15)S-7 (3), and Al0.33Sm3SiS7 (4), crystallized in the chiral and polar space group P6(3), have been prepared by a facile synthetic routine. Compounds 1-3 show strong second harmonic generation effects at 2.1 um with the intensities of 1, 2, and 3 being about 2, 2, and 1 times that of KTP (KTiOPO4), respectively. The calculated band structure of 1 implies that the optical absorptions of BLn(6)M(2)Q(14) and ALn(3)MQ(7) family compounds are mainly ascribed to the charge transitions from Q-p to Ln-4f (4d for Y) states. Compounds 2-4 exhibit antiferromagnetic-like interactions.