Fire twice over
There is no translation cost at all. Both want scope, both take the optimistic reading, both would rather have an interesting failure than a dull success, and neither has to explain any of it.
What doubling removes is contrast. A partner in another element would supply the objection, the cost estimate or the emotional consequence. With two fire signs the enthusiasm goes around unchecked, and the first serious external constraint tends to arrive as a genuine surprise to both. Neither is reckless on their own account; the recklessness is produced by the pair.
Mutable and mutable
Neither anchors. Plans are provisional by default and both parties prefer it that way, so the arrangement stays flexible far longer than most people would find comfortable.
The consequence is a shared life with no fixed points. Where to live, what to commit to, whether to have children: these questions can remain genuinely open for years, not through avoidance but because neither temperament experiences openness as a problem to be solved. Difficulty arrives when one of the two quietly changes their mind about that and does not say so.
Jupiter doubled
Jupiter rules both, and Jupiter expands. Two Jupiter-ruled people are generous with money, time and promises, and neither has an instinct for contraction.
Saturn is the placement that matters here, in both charts. Where Saturn sits, and what condition it is in, determines whether the pairing has any access to limits at all. Two charts with weak Saturns produce a household that is enjoyable and financially disorganised. One strong Saturn between them is usually enough to keep things upright.
What neither supplies
Maintenance, and the willingness to be present for something dull. Neither will volunteer for the tedious half of a shared life, and there is no third element in the sun signs to take it on.
The other absence is emotional depth on demand. Sagittarius handles distress by moving, physically or conversationally, so when one of the two is genuinely in trouble the other reaches for a change of scene rather than for sitting still. That reflex, doubled, leaves difficult things unattended. Grief and illness are where the pattern shows most clearly, because neither can be outrun.
Why sharing a sun sign settles nothing
Two people with the same Sun can be almost nothing alike. The Sun is one body, and the sign shared here covers a twelfth of everybody, so identical Suns give a shared appetite rather than a shared personality.
The Moon, Venus and Mars are usually where the real similarity or difference sits. Two Sagittarius Suns with opposed Moons live very differently from two with the Moons in agreement, and no sun-sign page can tell you which you have.
Questions people ask about this
Is it good to date someone with your own sun sign?
It removes friction and removes correction with it. Shared traits get amplified, including the ones neither person is managing well.
What do two Sagittarius people lack?
Anything that holds still. Neither anchors a plan or volunteers for maintenance, and no other element is present to take it on.
Does the doubled Jupiter cause problems?
It supplies generosity and no restraint. Saturn's condition in both charts is what decides how the finances and commitments actually run.
Are two people with the same sign alike?
Not necessarily. Moon, Venus and Mars differ freely between two people born under the same Sun, and those usually matter more.