Thanks Max, for that enlightning explanation.
I will try to answer your questions:
1: I read in the memoirs of either Lennart or his cousin Sigvard that after the accession to the throne of Gustav VI Adolf the king felt a bit embarresed to have two sons and one nephew styled plain mr Bernadotte. As the grandduke of Luxemburg hade enobled prince Oskar of Sweden in the 1890ies (he was a maternal uncle of that prince) after he lost his successionrights because of an unequal marriage the new king turned to Luxemburg again. I don´t know how close the two families were in 1951 but probably quite close. There is a difference thoug: prince Oscar was allowed to use the title prince (not of Sweden) but prince Bernadotte. His children were "only" counts/countesses of Wisborg. But lennart, Sigvard and Carl Johan were never styled prince Bernadotte, just counts of Wisborg. At least in Sweden! Prince Carl jr who lost his place in the succession in 1937 when marrying Elsa von Rosen was created prince Bernadotte but by his belgian brother in law king Leopold III.
2: Yes, as I wrote abowe, it was an initiative from the king.
3: At court Lennart, Sigvard and Carl Johan were styled and treated as counts of Wisborg after 1951. Members of the kings family but not the royal house. Sigvard pushed for having his princely titel aknowledged in the 1980ies but King Carl Gustaf said now. There were some strained relations after that. I guess the king would not do it because of prince Bertil who had sacrificed much of his personal happines and not married his Lilian until 1976 when rules were less strict. Bertil remained HRH prince of Sweden and Lilian became an HRH princess. In 1983 Sigvard started to call himself Prince Sigvard Bernadotte but this was not officially sanctioned by the king.
You are right about the unintroduced nobility. They have their own organisation and their own "peerage". In the swedish house of nobility - Riddarhuset - the membership is restricted to families enobled by swedish monarchs or families introduced centuries ago. The members of the unintroduced nobility are mainly from familes who emmigrated to Sweden in the 20th century. (Russian emigrés, east prussian nobilty, hungarian families, romanians etc)
I've taken part in a discussion on the European RMB regarding the appointment of Pr.Henry Battenberg as HRH by Q.Victoria on his marriage to Pss Beatrice, a title that was not recognized in Hesse and elsewhere in Germany.
I wondered about Count Lennart Bernadotte.
Born from an equal marriage, he lost his royal titles due to his morganatic marriage in 1932 to Karin Nissvandt, and became plain Mr.Bernadotte.
19 years later (Wikipedia info) Grand-Duchess Charlotte of Luxembourg admitted him in the nobilty of Luxembourg as Count of Wisborg with the treatment of Prince.
A couple of questions:
1. What was GDss Charlotte business to enoble Mr. Lennart Bernadotte 19 years after he had lost his titles ?
Were they close ?
Did he ask her for a title or did she decide to give him the title out of her good heart ?
2. Was the King of Sweden consulted about the concession of the lux. title and admission on the lux. nobilty ?
At least, did he not object ?
3. Was the title Count of Wisborg and the upgrade to Prince recognized in Sweden or did the swedish court continue to treat him as Mr. Bernadotte (despite all the kindness that seemed to have been between the present king and his family and the Lennart family) ?
The Wiki article has a reference to something I never have heard before: The Counts of Wisborg are considered to be part of the Swedish unintroduced nobility .
From what I understood, they are not "proper" swedish nobles, but correct me if I am wrong.