@Bl buddy Olivia fl was married to crown prince... As a married couple they may have consummated their marriage according to othe people but they didn't... So may be a child could be formed within 1 year...
If they did conceive a child and she marries the grand duke the royal heir would be considered as Duke's child... So the grace period of 1 year
If they did conceive a child and she marries the grand duke the royal heir would be considered as Duke's child... So the grace period of 1 year