In William Shakespeare's play King Lear, both Cordelia and Edgar are offspring who are undervalued by their parents. In both cases, this undervaluing is caused by two factors. The first is the parents' own blindness, which causes them to be susceptible to flattery and underestimate true merit. The second cause, in both cases, is greedy and dishonest siblings.
Cordelia makes the important point that good deeds are more important than flattery, and that one should suspect the motives of people who offer insincere praise, stating
If for I want that glib and oily art
To speak and purpose not, since what I well intend,
I'll do't before I speak- ...
Her warning concerning not trusting idle flattery is born out in her sisters' treatment of their father once they have been given their shares of his wealth.
Edgar, like Cordelia, is a loyal and legitimate son who loves his father. His illegitimate brother Edmund connives with Cordelia's evil sisters to get Edgar banished. Like Cordelia, despite his mistreatment, Edgar remains loyal to his father. Although the eventual fates of the two characters are different (Cordelia dies, Edgar becomes a king), their plot trajectories and characters, which emphasize loyalty in adversity, are similar.