I was surprised to see that a search turned nothing out, so here you go:
WI both the Dukes of Clarence (OTL William IV) and Cumberland (OTL Ernst Augustus I of Hanover) had died between 1820 and 1830? Depending on the exact timing, Frederick, Duke of York is either already six feet under or won't last past 1830 (he was born in 1763), as won't Charlotte, Princess Royal (the Dowager Queen of Württemberg - born 1766). So what happens next? Queen Victoria is minor. Who gets the regency? And how does Augustus Frederick, King of Hanover work (OTL he was the Duke of Sussex)?