Here are five passages from Fire in the Blood, the 4th book of the Brimstone Angels series by Erin M Evans, which I mentioned in my earlier reply to @MouseKeyboard@ttrpg.network. The quotes contain minor spoilers for the end of the eponymous book 1 of the series, and major spoilers for the content earlier in book 4. I would highly recommend both the series in general and this book in particular. This book and the two that follow if your interest is in political manoeuvring (this book on the politics of Cormyr, books 5 and 6 on the somewhat more exotic politics of the dragonborn kingdom of Tymanther). The series as a whole if you have any interest in the politics of the Nine Hells, or the interaction between a warlock and her devil patron, or what it's like to be a tiefling in the Forgotten Realms—a race that, by the Player's Handbook's own admission (at least prior to WotC's culling of so much excellent content a year or two ago) isn't innately evil in any way, but frequently gets treated as though it is.

The quotes don't go into cloning at all, but I don't think that a clone would be considered the same "person" as the existing monarch, and so a clone would probably take its own separate place in the line of succession. Probably not very high, given the existing laws' precedent of attempting to make the succession as straightforward and clear as possible, and minimising the ability of anyone to use magic to mess with that.

“Cormyr’s full of rules that don’t make sense,” Dahl said. “Commoners can’t wear more than one kind of feather in their hats, adventurers need special permission to hunt monsters, and if a king gets resurrected, they castrate him like a yearling and throw him out of the country, and his benefactor gets executed—gods only know what that’s about.”

“Did you not hear me?” Brin demanded. “You can’t bring him back.”

“I did, though!”

“No, I mean the law doesn’t allow it. A resurrected Obarskyr goes to the end of the line of succession—now I will be king before Irvel. He’s as good as dead to us.”

“Karshoj,” Havilar said. “Are you listening to yourself? Maybe he won’t be king, but he does get to see his family again.” Brin had the decency to color at that.

“You’re right,” he said. He rubbed his hands over his face. “Forgive me, that was … I’m reeling a little, is all.” He watched Irvel cross the clearing. “We can’t tell him.”

“I think he ought to know.”

“He might want to,” Brin said. “Or it might upset him—you don’t resurrect nobles in Cormyr. And he’d ask where you got such magic, and I can’t imagine he’d like the answer any more than I do.”

The laws about resurrection spells were, as many laws in Cormyr, tortuous and specific, crafted in reaction to ten thousand crises no one wanted to repeat. A resurrected noble lost all of their blood rights. Except a resurrected Obarskyr lost their place in the line of succession. Except a resurrected monarch was immediately deposed, magically neutered, and exiled from Cormyr, their would-be benefactor executed as a traitor.

Nausea suddenly overtook Brin. He dropped down on the covered steps of a boarded-up house and put his head between his knees. Foril was dead. So Irvel was king. And if resurrecting the crown prince was bad, resurrecting the uncrowned king was so much worse that Brin’s guts threatened to invert at the possibility. Suddenly, Havilar’s assistance wasn’t just threatening to make Brin’s life harder—it could actually get her killed.

Irvel blinked. “I blacked out a moment. And then Havilar was there. She’d healed me. She’s a good one,” he said to Raedra. “Whatever else is happening.”

“Your memory of the moment before you blacked out,” Ganrahast repeated, “is Aubrin Crownsilver trying to heal you, and the spirit of his father reaching out? And it’s very clear in your mind?”

“Yes,” Irvel said. Then, “I must have slept a little between then and waking up. I think I dreamed of Hal and my father and a great towering castle …”

Irvel stopped. A chill ran over him. Hal was dead and Foril was dead. And beyond the darkness of death lay the kingdom of Kelemvor.

“What day did they find you?” Ganrahast asked.

“I don’t remember,” Irvel said. But it hardly mattered—he’d seen Foril there. His father was already dead. By law, the crown prince was the king in all but the most technical matters.

And the king may not be resurrected.