This is a good example of a way the Chinese language is underrated. I had not seen the word "监护人" before, but I had seen "监" many times and so I knew the word had something to do with supervising.

Turns out I guessed correctly: 护卫着 is like "security guard", 监护人 is like "guardian (of a child)"

监 basically means to watch closely. You were basically right with the meanings of 护卫者 and 监护人。Except it is 护卫者 instead of 护卫着, the later means the verb guarding.