Gemini third decan

If your Sun sits between 20° and 30° of Gemini, this is your decan. You share your sign with everyone born across its thirty degrees, and you share this band with about a third of them.

Your two rulers

Triplicity: Saturn, reached through Aquarius. This scheme walks the three signs of your element in order, so a Gemini decan is coloured by Aquarius without becoming it.
Chaldean: Sun, from the unbroken run of seven visible planets that starts at Mars in the first decan of Aries and never resets.

The two disagree here: Saturn by triplicity, Sun by Chaldean order. Neither is a mistake, and averaging them would produce a ruler no lineage uses.

You have two rulers, not one, because two schemes exist and they disagree. Both are shown here and neither is blended into the other. The triplicity scheme walks the three signs of your decan's element in order, so the Aries decans are ruled through Aries, Leo and Sagittarius. The Chaldean scheme runs one unbroken cycle of the seven visible planets, starting at Mars in the first decan of Aries and never resetting when a sign ends. They agree sometimes and part company often. If someone tells you there is one correct ruler for your decan, they are picking a lineage without telling you they picked.

The other two Gemini decans

Sun also rules 4 other decans in the Chaldean run, which is what an unbroken cycle of seven across thirty-six bands produces.

What this calculation assumes

version: asternym-western-advanced-v1
zodiac: Tropical
decanSpan: Exactly 10°, three to a sign, thirty-six in all
decanRulers: Two schemes, both shown and never blended: the triplicity scheme walks the three signs of the element, and the Chaldean scheme runs one unbroken cycle of the seven visible planets from Aries I, never resetting at a sign boundary
decanGuardians: Not computed. The guardian-deity decans circulating online are a modern invention with no fixed date table behind them