I think I have at least one player who might want to have his magus settle down with a wife.
But the magus has the normal Gift, so that would penalise when finding someone to love.
But then, what happens if the potential love interest has Curse of Venus?
Would they be drawn to each other?
Curse of Venus just causes problems when it comes to love, it never helps. If someone suffering from the Curse does somehow manage to end up in a happy relationship, then it is despite the curse, not because of it.
The magus can extend their Parma onto others, so they could try doing that with anyone they attempt to court. I don't think time under Parma prevents getting used to a particular magus and their Gift.
Parma is indeed essential to have any chance of matrimonial harmony.
You are probably right that with the protection of Parma, the partner does not get used to the Gift, but they would get used to the particular magus (obviously I would say).
Thus the question is, why do some people learn to live with the effect of the Gift? This idea of «getting accustomed to the effect» is very 3ed IMO, when the entire cosmology was less well-defined. The 5ed very specifically says that the effect is supernatural and it is always there. I have interpreted that as good friends and close associates know rationally that the magus is trust-worthy, even though they emotionally feel otherwise (for supernatural reasons). The emotion never goes away by 5ed, but it can be suppressed by rational thought and will-power. Under this reading, a partner who is normally under Parma should be able to respond rationally when caught without it.
The point of Curse of Venus is that it creates unreciprocated love. Thus, the magus could well see someone with the curse get a crush in spite of their Gift, but that would not be the person they want to marry. Alternatively, the magus could get a crush on the cursed one, who would not be interested, and given the Gift doubly not.
The obvious story for a curse of venus'ed partner of a magos is that someone else catches their eye. Someone entirely inappropriate. So they cheat on their husband/wife with the new person who of course turns out to be a faerie/demon/rival mage/young nobleman. And of course maybe a pregnancy is involved and suddenly you've got complicated fae blooded/changling/line of succession/etc issues to work out.
Curse of Venus just brings you trouble in your love life so a marriage to someone with it is going to be a train wreck. What could be fun is if the two partners are genuinely in love and always find a way to reconcile, but that the Curse of Venus causes constant issues with cheating, awful suitors, etc. All the covenfolk get used to the constant fighting and making up, its just all drama.
If the person you are seeking out has curse of Venus this could, theoretically, help you only if it would cause them trouble. For example you are attracted to a woman whose father has an abiding fear of magic and will disown her if she is in a relationship with you, so of course she falls for you. Or she is already married, so on and so forth.
Imagine a Mystery Cult requiring these sorts of things. Or an Ex Misc lineage.