[stvltvs]

I think this is straining the meaning of false friends. They are derived from closely related forms and differ only slightly in meaning: "to us two" versus "to us all". I guess if you see that as a significant difference, but a more typical example would be English parents vuersus Italian parenti meaning kin.

[tsimionescu]

I would argue that parents / parenti are also closely related meanings and closely related forms (and Italian parenti ultimately derives from the exact same root as English parents, the Latin parens meaning either parents or more generally ancestors). In contrast, uns and unc derive from separate PIE roots, while the semantic distinction was important in both PIE and Old Germanic.