Richard II of England was childless which was one of the causes of the future War of the Roses between the House of Lancaster and the House of York.
When Henry IV deposed Richard II in 1399, he assumed the crown due to being the son of John of Gaunt, the 3rd son of Edward III and therefore claimed the throne through direct male descent from Edward III who made a decree in 1376 limiting succession to male heirs.
Wikipedia states that Edmund Mortimer, 5th Earl of March “was heir presumptive to King Richard II of England, his first cousin twice removed, when Richard II was deposed in favour of Henry IV.”
That was because he was the son of Roger Mortimer 4th Earl of March(died in 1398), the son of Phillipa of Clarence, the daughter of Edward III’s second son Lionel Duke of Clarence and thus senior in primogeniture making it appear that Richard II overriden the decree of Edward III.
His sister Anne Mortimer married Richard Conisburgh, 3rd Earl of Cambridge, son of Edmund of Langley, 1st Duke of York, causing the House of York to claim the throne during the War of the Roses.
However the Wikipedia article on the War of the Roses that “at the onset of Richard II's reign, Gaunt was the official heir presumptive, but due to the intrigues of his turbulent rule, the succession was unclear by the time of his deposition.”
Did Richard II officially name Roger Mortimer 4th Earl of March and later Edmund Mortimer as his heir or did he make the succession unclear?