Hi,
I think Marie and Ferdinand would get along with George and Olga, as they were cousins of varying degrees.
Marie offered Olga refuge after the revolution but I can't remember whether Olga accepted or not.
The main reason for any anomosity would have been in the next generation.
Carol of Roumania married Helen of Greece and that didn't work out. In fact, Carol treated her very badly.
George II of Greece married Elisabeth of Roumania and they didn't like each other much.
This should have been a grand uniting of royalty (a Roumanian brother & sister marrying a Greek brother & sister) but it just desolved into a royal feud.
Pity...
Larry