I like the above idea.

The Siblings' Rings

Suratisia Koban came to the throne as Monyadaki III, known as The Reconciler for her inniatives which gave the losing sides a measure of power in the government.

But she was wracked with guilt over the murders of her siblings by which the path to her throne had been paved. Thus she created five magic rings, one for each of her children.

To her eldest she gave the Ring Of The Dragon. It is a powerful magic item which is believed to grant the wearer the following powers:

Magic Resirtance 10

Additional Sorceror spell slots at levels 0-4

+1 Sorceror level. (If the heir has no sorceror levels the wearer can use the cantrip spell slot only.)

The ability to Alter Self into a dragon once per month.

The other four rings were cursed to prevent all spellcasting.

All five were cursed to make it impossible to remove them. The idea was that it would prevent her children from being forced to kill their ambitious, (or guided by ambitious nobles,) siblings.

The actual result was that Kuaari the Unlucky survived his mother by 13 days due to poisoning. With his siblings unable to inherit, the Monyadaki Dynasty ended in only three generations.

The rings have shown up from time to time, but they all look alike so no one knows which is which. There is a rumor that The Ring of the Dragon is among the Crown Jewels, but no monarch will dare to try it on for fear that it is actually one of the Siblings' Rings.