There was a time when I said something like
Mi havis monadon kiel dorlotbesto, kiam mi havas 12 jarojn.
But then someone corrected me, saying that it should be havis, instead, and showed me a corroborating page from the PMEG (I do not have it at the moment). Should verbs in some subordinate clauses not be relative? I remember that the page mentions some ki-vortoj like "kiam", "kie", "kiel", and a couple more, but, if I remember correctly, not "ke", "kiu", or "kio". What is the rule here, for relativity of tense?