Just like the Bahuns you have known, Kumais may also be Uphadhaya, Jaisi or even Kshetri. They were originally from Kumaon region and thus got this name of their clan. However, there is a false and derogatory definition of 'kumai' (not suitable to mention here) also very popular among non-Kumais. That is one of the reasons why Kumai are considered inferior by non-Kumais. Shivakotis are Kumais for sure.