Pieter is always full of praise for his late mother-in-law, who indeed was the only one who supported him. Even his own mother had her reservations due to the difference in rank.
Coincidently I bought the book on Biesheuvel this weekend! It says that it was Juliana who called Biesheuvel on March 14th 1966, a few days after Beatrix' wedding. She wanted to discuss 'difficulties' around the upcoming wedding. Biesheuvel and his cabinet were busy for weeks with the matter. In the cabinet only Defense Minister Piet de Jong (a year later Prime Minister, in the 50/ties he was an aide-de-camp to Juliana) was in favour. The Queen was against, she thought it was oldfashioned and un-Dutch.
Pieter held a plea (the book is not clear when, but I assume at an earlier stage) to prime minister Cals and minister of state Beel, without result. After that he turned to Biesheuvel. Biesheuvel was sympathetic but told him: 'you fell in love with the wrong girl. he did not mind Pieter being a commoner "he was a decent young man from a decent family" but he did admit that he might have felt differently had Pieter married the heiress.
Pieter telephoned Biesheuvel on March 15th (a day after Juliana) and wanted to meet Biesheuvel the same day. They met at the ministery. Biesheuvel noted that until that stage Pieter never thought about a title but because of Beatrix' wedding to Claus he started to think differently. Claus was accepted as a Prince by the people, why wouldn't that be the case for him? 'Claus yes, me not'. Biesheuvel spoke again to Beel and to Juliana but the outcome was not changed, even though the children would be princes.
Note that in 1998 the diary of PM Cals became public. And there it was also said that it was Juliana who stopped the title for Pieter, while he tried to insist on it. In 1998 Pieter wrote a letter where he denied having lobbied for a title, and says that it was twisting facts.
In 1999 Biesheuvel did an interview with a newspaper and mentioned the lack of title for Pieter was 'discrimination'. A word supposedly used by Pieter in 1966 as well.
Biesheuvel and Pieter became friends. At Pieter's 60th birthday Biesheuvel made a speech where he said that Pieter never became a Prince and that Pieter and his wife never wanted that in the first place: 'it was your own decision, after confidential councils with good friends.'
A year later he told Pieter's biographer Dorine Hermans that at one point Pieter and Margriet preferred a title, but not in the pushy and lobbying way as has been described by the Volkskrant. It had to be regarded in the negative light with which Pieter was received at court, and they were wondering how he could keep himself standing in such an environment, doesn't he need to have a certain status for that? Not to be treated as a second rate character? Hermans said that after these revelations -slip of the tongue perhaps- Biesheuvel closed like an oyster, as if he had said too much.
The reality is that he was treated as a second rate character for years and he had a difficult personal time, especially in the 1970s.