In the most stable monolayer boron sheets predicted so far,there exist two kinds of hexagonal holes,i.e.,the isolated hexagonal holes and twin-hexagonal holes.[1] Our previous ab initio study shows that planar B18Hnq (n= 3-6,q= n-4) clusters possess a double-chain framework with a hexagonal hole at the center.[2] In this work,we performed an extensive DFT calculation which shows that the 2+ "glasses-shaped" D2h B26H8,B26H82+,and C2 B26H6 (Fig.1) are the smallest hydroboron clusters featuring a double-chain framework with a twin-hexagonal hole at the center.Detailed nucleus-independent chemical shift (NICS),electron-localization function (ELF)[3],and adaptive natural density partitioning (AdNDP) [4]analyses indicate that these species are overall aromatic in nature,with the formation of islands of both σ and π aromaticity (Fig.2).These bicyclic hydroboron clusters,together with the previously reported monocyclic B18Hnq clusters,[2] establish the molecular basis for the modeling of short-range structures,nucleation,and growth processes in monolayer boron sheets.