He has to claim the credit in order to transfer it to you. He claims the credit, and you put the transfer information on your return.

This TurboTax Canada FAQ tells you how you can claim a DTC transfer on your return: How do I claim the Disability Tax Credit transferred from my dependant?
 

I had the same query, as there seems to be no place on the tax form to indicate the amount of the disability tax credit that is being transferred from the person with the disability to the one who is claiming the credit. I find it odd, that since someone with a disability is allowed to transfer the credit, that there's no section on their tax return indicating that's been done, or how much has been transferred. The way it stands now, it looks like the credit is being used on both the transferees and transferors tax returns. I believe it would be clearer if the CRA or turbo tax would add a line under the federal non-refundable tax credits section, stating disability amount transferred to a supporter/caregiver. That would make it clear that a transfer is being done and also the amount that's being used from the credit. 

@user17757538589 When you enter your dependant into your tax return, you'll be asked about their Net Income. TurboTax will use that info to determine how much of the disability tax credit can be transferred.

And yes, the disability tax credit *is* being used on both returns. The disabled person must claim it on their return, and the caregiver will claim whatever is transferred.