Mixing Help blending vocals together

Hello Sonar users,
I recorded my wife and sister-in-law on a track together, it's a song we are doing on our project that they are known to sing together locally years ago.  Well my sister-in-laws voice is not the same due to smoking :( so there are notes that she struggles with.  My wife’s voice is similar in places so we recorded my wife singing those parts.  Well the levels are not quite the same, I got vocal rider by waves hoping that it would help but it doesn't.  Has anyone worked with blending vocals recorded at different times.  A thought that I'm thinking is to export vocal and use the program Wavelab, but is there a way to do this in Sonar with out exporting?
 
I'm using Sonar Platinum....

Vol Automation would be my first stop for mixing in the new vocal parts.  And as Zargg above, vocalsync for timing.
 
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Melodyne will fix notes that are off, but if the smoking voice is harsh and raw, Melodyne will only fix so much.
timber in ones voice is best treated with EQ.
Vocal Synch will help glue them closer together however, what I have found is if they are way off, too much Vocal Synch can produce artifacts.
 
as for the levels, compress them both. then as mentioned previous, use volume automation.
if you need to be surgical, use nodes and draw them in. its almost like fader riding in the older days.
you can use Vocal rider but I find it just typically blends them all together and in some cases that's not what we want,
we want some vocals to sit in the back at certain times and others to stand up front, then vice versa.
the only way to accomplish this is through volume automation. which in my opinion...
is one of the top 5 tools a digital audio editor has.
 

All vocal sync does is line up the timing of the guide track with the processed track...

Apart from pitch correction, at least full Melodyne also has a pretty musical amplitude/volume correction.