bonded pair of cockatiels

Question
Can I seperate my two cockatiels that have been together for a couple years and have had some eggs and two babies together.  The last couple times they had eggs they killed the babies though.  

Answer
If they have only been together for a couple of years and have killed the "last couple of clutches" (which makes me believe that they raised at least one clutch sucessfully)- you are probably breeding them too often.

Birds should be limited to one clutch a year (or two at the very, very most).

I would recommend leaving the birds together so that they don't get lonely (birds are extremely social creatures that need attention daily either from a bird companion or a human friend), but I would recomove the nest box (to give them a break), and I would recommend the following tips for discouraging them from breeding any more:

http://www.forthebirdsdvm.com/breedingbehavior.htm

I hope this helps answer your questions.

-Maggie