From what I can see, they seem to be regarded as unrelated. Wiktionary  says of the word for "teach": "Possibly from Latin monēre (“to remind, advise, teach”), with phonological influence from mūnire (“to defend, protect”).", while for the "people" word, MacBain  says:
"household, people, Ir. [muinntir], O.Ir. [muinter], [muntar]. This is regarded by Stokes, Zimmer, and Güterbock as an early borrowing from the Lat. [monasterium], monastery; the word [familia] is often applied to monasteries by Irish writers."
It's not clear whether they are cognates. If they are they are actual cognates (words in different languages with common origins). I think you mean "false friends," words that are similar in appearance (often because they are cognates), but have different meanings. A classic example of a false friend is Spanish embarazada, which means pregnant, not "embarassed." https://en.wikipedia.org/wiki/False_friend