Guardians Of Order Online Discussion Forums – A quick Question!!!
There are three generations between Lintra and Merlin, all of them attempts at producing a ‘human’ surrogate to wed to an Amber prince.
Dara III is the one that finally connects with Corwin. But—back in Chaos, it is Dara II that is raising Dara III’s child Merlin in a fast-time Shadow, so that Dara III can be off trying to get access to the Pattern.
Dara III is the one who switches sides with Oberon’s help.
Dara II is the one who doesn’t—and becomes Merlin’s “legal” mother later without ever clueing Merlin that his real mother was imprisoned for betraying Chaos in PatternFall.
Hence Dara the Younger and Dara the Elder.
* I believe the Double Dara theory was first proposed by M on the Amber Mailing List.
** As pointed out by Michael in the comments, this is also a way of supporting the very different ‘tone’ of Dara, Corwin series, and Dara, Merlin series.