KBi2, RbBi2, CsBi2 belong to a large family of cubic Laves (C-15) superconductors. The SuperCon database lists 192 C-15 superconductors, belonging to 16 different chemical systems, with critical temperatures ranging from 0.7 to 10.7 K. However, the three Bi-based compounds distinguish themselves from the whole family in a number of ways. Firstly, besides LaAl2 (Tc ≈ 3 K 75 ) and LaMg2 (Tc ≈ 1 K ), they are the only main-group element-based Laves superconductors. Secondly, we have shown that in RbBi2 and CsBi2 systems the superconductivity clearly emerges from the electron-rich Bi pyrochlore lattice, with Rb/Cs acting predominantly as electron donors to the Bi lattice. Such clear picture is not possible in case of transition metal based systems, where the bonding between atoms occupying the two crystal sites is expected to be much more metallic. Lastly, Bi is the heaviest stable element (Z = 83) and the relativistic effects on electronic properties in KBi2, RbBi2, and CsBi2 are the strongest of all of the Laves superconductors, even when compared with Ir-and Au-based systems, such as (La/Lu)Ir2 76 and (Pb,Bi)Au2 , since the SOC effect on 5d valnce electrons is weaker than on 6p shell.