What the house does to the Sun
This placement puts the Sun on the descendant end of the chart, as far from the ascendant as it can be. The effect is that self-definition arrives through relation. Left entirely alone, this person is not so much lonely as unresolved, and they generally know it.
The house covers marriage, business partnership, contracts and declared enemies alike. What unites them is that each is negotiated with a named other party, in the open, on terms.
How it shows in a life
It shows in a life where the major turns are dated by relationships rather than by jobs. It shows in unusual skill at reading a room, since attention has been pointed outward from the start.
It also shows in rivalry. The tradition is blunt that the seventh gives open opponents, and charts with this Sun frequently contain one long-running adversary who did as much to shape the person as any friend, and is described decades later in surprisingly warm terms.
The cost of the placement
The cost is dependency. A person whose identity forms in company can drift a long way toward whoever they are currently with, and the correction usually arrives only after a partnership ends badly.
The second cost is the avoidance of open conflict, which this placement often mistakes for diplomacy. Contracts and disputes are both seventh-house matters, and dodging the second while relying on the first is not a stable arrangement.
The opposite house, and why it matters
The first house sits opposite, holding self-presentation and initiative. The axis is the whole question here: how much of the self exists before anyone else is in the room. A Sun in the seventh with a strongly occupied first manages the balance easily; without that, the chart usually describes someone who found themselves rather late, through a specific person.
Why a house placement needs a birth time
The seventh cusp is the descendant, the ascendant's opposite point, and it slides at the same awkward rate of about a degree every four minutes. An hour's error leaves this Sun in the sixth, where the life is about the job rather than the person, or in the eighth, where it is about what is shared and what is owed. Three quite different biographies.
Where the record is a recollection, treat the sixth, seventh and eighth house readings as candidates, and let the pattern of the adult life rather than the appeal of the description choose between them.
Questions people ask about this
Does this placement guarantee marriage?
No. It says partnership is a major theme, which is as true of people who deliberately avoid it as of people who marry twice.
Why are enemies in the house of marriage?
Because the tradition classes both as the person openly opposite you, bound by declared terms. Hidden enemies were assigned to the twelfth instead.
Which planet should be read with it?
Venus as the natural ruler of the seventh, and the ruler of the sign actually sitting on the descendant.