Saturn is natural to the MC/10th, so it does not indicate 'absence' of anyone if placed there.I have Neptune in the 3rd and my only sibling does not have addiction issues. Neptune represents many things, but should not automatically be associated with 'addiction' because of its association with drugs. Drug users most often are not addicts anyway. We slap that term onto others' behaviors we tend to jump too quickly to judge/categorize.
These are loose associations that do not hold true most of the time.
Yes, what you've asked about is generally true. Sun-Saturn together can indicate a serious or controlling parent/father. I have Sun conjunct/parallel Saturn and my father has Saturn conjunct Asc and is serious, conservative, and quiet. Most of this is associated with parents, somewhat with partners.
Don't make too big a deal of it. Your birth chart is yours, and is about you, your challenges, your development. Own it.
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The Declinations Guy
Astrology & Natural Medicine blog