But Tatiana can marry her Prince.
Carina cannot marry hers.
Yes she can. She can 100% absolutely marry Gustav. Tonight, tomorrow, next week.
They can marry any time they wish. They prefer to shack up and play house.
A tiara is a piece of jewelry, period. If Gustav's parents think it provident to let her play with the jewels, then it's up to them. I mean, I'm sure that the jewels are well insured, just as I'm sure that every piece of real estate is carefully locked up so that it is not squandered. I think that the will itself is proof positive that this family is determined to hang on to its wealth.
I think the far, far greater sin here is that Gustav has two sisters who have no inheritance rights. Gustav has a 100%
choice in who he can marry. His sisters had no rights in
choosing their sex at birth. Because they are female, they lose out. If anyone has a gripe, it should be their gripe.
The next heir in line for this little branch has married equally, to someone who has a gainful and independent career; they have a legitimate son. The next heir genuinely believes in the Protestant faith that the grandfather's will provides as a requirement, and in fact very active in it; he has offered his own family schloss as an international conference site. Things will be fine in that family in the next generations.
So they don't get married - so what? This really isn't a tragedy in the least. They have money, they have a nice place to live, she gets to wear pretty clothes and they both get trotted out in front of cameras for "family" events. It really doesn't seem to be all that dreadful of a situation. In fact, it seems rather nice to have all that and very little to have to do to earn it; they have no public responsibilities (unlike Royal families with full calendars) and whatever they choose to do, like open the hunt breakfast, is purely by choice. (The only obligation that Gustav had was to marry in accordance with his grandfather's will, and he seems to be a failure in that.)
And - they can always get married. Yes, they can. Sure, he'd have to, you know, work for a living and all; but there are a lot of princes who do and it doesn't seem to have done them too very much harm. I also wish to point out that Gustav's father is still alive, still reigning Prince, and one of the 400 wealthiest individuals in Germany. I doubt that if they married, that Gustav would in reality have to work; I'm certain his father is in a position to provide a jointure to provide for them amply if not splendidly. There are several subsidiary properties owned by the family that would provide housing far in excess of what the majority of the human race - or even the posters here - have over their heads.
Gustav's girlfriend is by and large a creation of her press agent, and if one takes a careful look at, for instance, the arc of pictures released over a two year period of time from one Royal interaction, that press agent earns his pennies. This whole "tragedy" of not being able to Marry the Prince seems to me to be overly-turgid.
Because - and I'll say it
again - Gustav and she can marry at their convenience and leisure.