"Unicorn" is going to feel, sooner or later, that she's being treated as a sex toy to spice up your relationship. And I can't think of a single way I could convince her that's not the case.
Oh, well, as long as you and your wife are happy, who really cares if you treat another person like a sex toy.
That was sarcasm. In case you missed it. Because apparently you've missed that she's being treated like a sex toy.
I disagree, WhatHappened. You seem to be jumping to conclusions. This triad involves 2 women who have been platonic friends for years, long before they had sex. So obviously it's not a case of a unicorn just being used for sex.
This triad has had long weekends and longer vacations together. Of course, they are not having sex constantly on these vacations. Of course, they are sightseeing, going to the bathroom, eating, shopping, talking, driving or walking through airports, flying, arranging accommodations, etc., etc.
I am still waiting for an answer as to whether there is much non-sexual bonding date time, one on one, with Wife+Unicorn alone, or Titanic+Unicorn alone. Surely there are times on vacation where Wife or Titanic are otherwise occupied, sleeping, showering, running an errand, and so Unicorn is left alone with one or the other of her lovers. And I suspect long term female friends will enjoy doing some girly shopping that Titanic isn't interested in now and then.
If this is the case, is that seen as threatening to the marriage of Wife+Titanic? If not, why not? If it is, why? If it's OK for any 2 dyads to have one on one time, why is sexual intimacy one on one with only one member of the original couple seen as threatening?
I think if Titanic wants one on one sex with Unicorn, he should be asking both his partners about the nature of the actual threat one on one dates, romance AND sex is imagined to be. Where does the threat lie? Why should it be distancing?
After all, if 3 people are friends, they MAY enjoy most when all 3 are together. But they also enjoy when just 2 of the 3 are together. It may actually be a relief to just be the 2 of them now and then. It gives you time to get to know each other in a different way.
And of course, some friends of friends do not get along. Sometimes I have had 2 friends whom I loved dearly, but these 2 friends didn't really click. Because they each satisfy different interests I have, but they don't necessarily share those interests with each other.
I think this thread is a case where monogamist thinking is still hanging on in a polyamorous situation. The Wife thinks: sex between the married couple is sacred. The sex, and the bond, of the married couple is paramount. Therefore, the married couple can have one on one sex whenever they want. But the sex and bond with Unicorn, while fun, is just not as important as the marriage bond. Therefore it doesn't need to be nurtured by one on one time, either romantic or sexual.
I'm of the opinion that one on one sex is more intimate than any group sex could ever be. Wife seems to agree. So she's hellbent on limiting one on one sex to just her and Titanic. Unicorn just isn't allowed to have this privilege. Wife and Unicorn seem very fearful that somehow if Unicorn has one on one sex with either of her lovers, the original marriage will automatically fall apart!
We poly folks who are in a couple, but date others separately, know that one on one sex with our OSO(s) does not automatically cause a rift in the original couple, as long as the original couple continues to nurture their relationship with romantic dates, proper scheduling of meetings or texting, phone calls, etc., with other lovers, care taken as to finances for dates, and childcare arranged so one partner doesn't feel like they are left behind babysitting while the other partner is out having adult fun. Any one member of a poly couple should make sure their original partner will be OK while they are gone. They've done their chores and errands, there are supplies in, there's a set way to check in on the phone, either for a goodnight text, or for emergencies.
In fact, although my partner Pixi and I usually date separately, we have experimented a bit with threesome or foursome sex with a couple of my bfs. The worst part of that was my bf getting distracted by NRE sex with Pixi (or another female friend we had there for that foursome), and neglecting me. So it caused a rift between me and the bf who neglected me, not a rift between me and Pixi. It actually brought Pixi and me closer, because she saw I was hurt, and she shared my anger after the fact, at how the bf neglected me to spend more time focused on pleasing himself with her, or pleasing her (or the other woman we had the foursome with), leaving me hanging, turned on and unsatisfied.
That doesn't seem to be the case here. Titanic doesn't seem, during sex, to be bad at making sure Wife is satisfied even though Unicorn is also involved in the sex. He doesn't seem to be letting his NRE run wild, and be neglecting Wife. This should be reassuring to Wife, that even if Titanic and Unicorn have one on one sex, somehow she will be neglected and maybe even abandoned completely, divorced, just because Titanic and Unicorn have sex occasionally without her. And likewise, Unicorn and Wife aren't having one on one sex, because they have an erroneous belief that this will cause Titanic to feel neglected, and fear complete abandonment. They don't believe he is absolutely fine with any one on one sex, involving him, or not!
And it's been going on for 9 months. The women are very stubborn! Why aren't they hearing Titanic's wishes? Why are they putting their own fears ahead of his desires and reassurances?