In his heart, Riku had known that his parents were still alive, and would write him as soon as they were able. (Corin had assured him, they were alive when he left)
But that white envelope in his hand, that was their actual reply. What if they were disappointed in him, of what he'd become. His and the Prince's feelings for each other aside, he WAS sleeping with the Prince on a promise of love and marriage. If he was a woman, he'd be an utter disgrace to his family.
"I just... need a moment," Riku begged, hoping Corin would understand. "They have been nothing more real than a dream for so long."