Does this sound familiar?
From Spenser’s Faerie Queene, an opening scene similar to Leir is played: The eldest Gonorill gan to protest,
That she much more then hew owne life him lov’d:
And Regan greater love to him profest,
Then all the world, when ever it were proov’d;
But Cordeill said she lov’d him, as behoov’d:
Whose simple answer, wanting colours faire
To paint it forth, him to displeasance moov’d,
That in his crowne he counted her no heir,
But twixt the other twaine his kingdome whole did share.
(Bullough, 333)
The first mention of Cordelia’s death by hanging is introduced by Spenser, and was probably here that Shakespeare received the idea. After replacing King Leyr to his throne, Gonorill and Regan have her in imprisoned where, "Through proud ambition, against her rebeld, / And overcummen kept in prison long, / Till wearie of that wretched life, her selfe she hong."
http://king-lear.org/spensers_the_fairie_queen