Which Daeron Targaryen was Bran referring to in his talk with Tyrion? As far as I know there were three famous Daeron's:
- Daeron the Daring, Brother of King Aegon II
- Daeron I, The Young Dragon
- Daeron II, The Good
Prince Daeron 'The Daring', son of Viserys I, didn't have any nephews who were crippled. His nephews were:
None of the Seven boys were crippled.
King Daeron I 'The Young Dragon' was the eldest of his father's children. Neither his brother (Baelor the Blessed) nor his sisters (Daena, Elaena, Rhaena) had any children when King Daeron died young. Only his sister Princess Daena the Defiant had a son but that was after the King had died and his brother Baelor had taken the throne. Nevertheless, that Child was Daemon Blackfyre (And realm would have been better served had he been a cripple).
King Daeron II 'The Good' had no trueborn brother. His only brothers were his half brothers chief among them Aegor Rivers, Daemon Waters (Blackfyre) and Brynden Rivers.
Daemon sired children, that much we know. But out of 7 sons of the Black Dragon, 5 are known and there wasn't a cripple. The youngest two sons of the Black Dragon are unknown so we can't say if either one of them was a cripple and I doubt GRRM told D&D about this minute detail about Kings who are not related to GoT and have no impact on the story they are dealing with. For what it's worth, not even GRRM knows what he wants to do with the youngest black dragons.
Daeron II's only trueborn sister Daenerys had married the Prince of Dorne, Maron Martell. Since she made the Water Gardens for her son to play in and since the current princes of Dorne are descended from her, it is unlikely that her son had a handicap like Bran. But Daenerys had other children as well so it is possible that one of them may have been handicapped and Daeron II was of scholarly disposition. Nevertheless, what's true for Blackfyres is also true for Daenerys' children.
Shiera Seastar, Mya Rivers, Gwenys Rivers (Daeron's bastard half-sisters) didn't bear any children that we know. Same is true for Brynden and Aegor Rivers.
In all probability, This Daeron seems to be another show-only King and should not be confused with books characters. But if it had to be any Books character, King Daeron II is the most plausible candidate solely because there are still a number of his nephews that we do not know about.