俱

Left person radical, the side form of 人. It indexes 俱 in the people-doing-things family: 你, 他, 们, 体, 信, 修. 俱 means 'all together, in company,' so the radical points exactly at the social meaning — a person doing something alongside other people. The plurality is in the radical, not the phonetic.

Right side 具 supplies the sound directly: jù. Same phonetic powers 惧 fear, 飓 hurricane. 具 itself depicts two hands lifting a vessel — assembling, providing, having ready. Faintly semantic too: 俱 carries that 'having it all assembled' flavor, used when a group is gathered with everything in place (万事俱备 'all is prepared').