It wasn't just Rhaenyra that Viserys had a large number of regrets about. As a boy, his father, Prince Baelon the Spring Prince had told him that he should be loyal to his family and to his brother above all else. Viserys had failed this with epic proportions. He had put a traitor who plotted against the Targaryen's above everyone, including his cousin-wife Aemma and his beloved little brother.
He now knew that Daemon never wanted the crown but a place in court and in his brother's heart. Hells, if Daemon wanted the crown so badly, he could have put forth his own name and raised an army to back him. However, Daemon didn't put his name forward and raised an army against his favorite cousin to support his brother. Daemon actually listened to their father.
Despite how poorly Viserys treated Daemon, Daemon stayed loyal to him for many years and only finally gave up on returning to court after Viserys banished the one person Daemon loved most, his niece, Rhaenyra. Even while Viserys ignored his little princess, Daemon doted on her and gave her the attention that her parents refused or were unable to provide her. He taught her their ancestral language, took her on her first dragon ride and taught her how to control Syrax. Hells, Daemon was the one to pick and place the dragon egg in Rhaenyra's cradle to begin with!
It had been 36 years since Viserys had seen, spoken to or even seen his brother's handwriting except for in his dreams and honestly, the King was lonely and missed his little brother.
Knowing that Daemon had completely given up on Viserys, Viserys knew that if he was ever going to see his little brother again, he had to reach out to him. Viserys broke their brotherhood and so it was up to him to attempt to fix it.
Yet again, Viserys asked a healer to record his words.
Daemon, my dear brother,
It has been nearly a lifetime since I have seen your face and felt your presence except as a specter reminding me of my many failings and in my dreams.
Brother, the Gods' have shown me that you have built a wonderful life for yourself where you are very happy in Volantis. I know Laena makes you very happy and I know you are a far better father to your six children than I ever was to Rhaenyra. Hells, you're a better husband by far to Laena than I have been to any of my overly abundant wives.
I'm dying Daemon and soon I will have to face the Gods' for all of my failings alongside our parents and forebears and I know that they are not pleased with me. I have failed you. I've failed to defend you, honor you or protect you despite how much you tried to do all of that for me.
I know my council wishes for you or any of your children or grandchildren to return to Westeros to take the throne when I'm gone but I also know you won't. You've never wanted my crown but rather my love and I've foolishly never honored that.
If I could, however, make any final request of you, in these, my final days, it would be that I wish to see you one last time. It has been far too long since I have seen your face and I wish to hug you one last time before I meet with the Gods'.
With deepest affection,
Your brother,
Viserys