Venus in the 7th house synastry means their Venus falls in your 7th house: where their affection lands in your life. What it feels like from both sides, the gift, the shadow, and how to find your overlays.
Their Venus in your 7th house lands on the house of partnership and marriage, the place in your chart that describes the partner you are looking for, and they tend to look like that partner. You feel chosen, and they feel they have found someone worth committing to. Astrologers watch for this one in marriage charts.
Their Venus in your 7th house
You recognise them. The 7th house holds your picture of the other half, and their Venus sits in it, so early on there is often a sense of "this is what I meant" that is hard to explain to friends. They are agreeable in your company, quick to compromise, and interested in the relationship as a thing in itself: the anniversary, the plans, the two of you as a unit. Your partnership instincts sharpen and you become a fairer, more attentive partner in return. Seen from their chart, you are the one they want to be paired with. They enjoy being your plus-one, they like how the two of you are seen together, and they tend to bring out their most gracious self for you. Conflict is usually handled softly here, sometimes too softly.
The gift
Commitment comes easily and feels like relief rather than sacrifice. Decisions get made as a pair, fights end in agreements rather than stalemates, and other people tend to treat you as a couple quickly because you behave like one. If you have a history of choosing badly, this overlay can show you what being with a genuinely willing partner is like. They get a relationship that fits, and a partner who reflects their best qualities back at them.
The shadow
Peace at any price. Both of you can become so invested in being a good couple that nobody says the true, awkward thing, and problems get filed under later. You may lose track of where you end and the relationship begins, deferring on restaurants, then holidays, then careers. They can be so agreeable that you struggle to learn what they actually want, and a Venus person who has swallowed too many preferences tends to leave suddenly.
Working with it
Disagree on purpose now and then about something small, so both of you stay in practice for the big ones. Keep one friendship, one hobby and one opinion that are entirely yours. When they say they do not mind, ask again, because they often do. Put the relationship in the diary like a third person: check in on it, review it, decide things about it together rather than drifting into them. Fairness is this overlay's native language, so use it.