And Carl and Ingeborg where also close related as her mother Lovisa was Carl's first cousin.
Found this article in "Majesty".
As I suspected, relations between Sweden and Norway were still in the freeze.
Haakon and Maud had nothing personal against Martha, but they weren't sure about the wedding given the fact that Olav and Martha were first cousins, Martha being the daughter of Ingeborg, Haakon's sister.
Haakon and Ingeborg's father, Frederick VIII was also the brother of Q.Alexandra, Olav's mother.
Prooving that the objection was the close relation between bride and groom, Haakon and Maud favoured a wedding Olav-Ingrid of Sweden - 2nd cousins
Martha was a royal princess.
She came from the "arrivist" house of Bernadotte who reigned in Norway until the independence under Olav's parents.
Was there a general anti-swedish feeling against the hatred Bernadottes 20 odd years later ?
Or was the wedding seen as the seal of good relations between the two countries ?
As to the opposition to the Harald/Sonja wedding, afaik, it was the fact that Sonja was a commoner and the king wanted a royal bride for his son.
After all, Norway had a new RF, his first queen was Edward VII's daughter, a very prestigious alliance, and Olav may have wanted to strenghten relations with other RF's to gilf the blason.
I guess he would wholeheartly welcome his marriage to Sofia of Greece.
Knowing that Norway abided to the salic law at the time, were there any pressions for Harald's sisters to marry someone of their rank ?
King Baudouin could be a good match (despite the fact that they were 1st cousins)