I have entered 50% rental ownership for both myself and my wife but turbo tax allocates more than 50% of the net rental income to my wife (the higher income earner). why?

Did you claim any Capital Cost Allowance (CCA) on the rental statement?

I did, assuming Turbotax would apportion the costs 50% as it does with all the other rental expenses.  Apparently this is not the case.  I went back and created another CCA table for my wife and put half the allowable CCA costs in hers and half in mine.  Now we both have the same net rental income.  Seems a little cumbersome but there you have it.

As CCA is an optional claim, the software requires you to make separate entries for each owner if they choose to make the claim.