It depends -
If you no longer have title to the rental property that you gifted to your relative, then you will not check the box that the property was sold/disposed of in 2017.
You don't need to report the gift of a rental property on your income tax return because there wasn't a taxable event (i.e. gain or loss on sale or disposition). You just need to report it on Form 709 United States Gift (and Generation-Skipping Transfer) Tax Return).
Any "built-in" gain or loss has passed to your brother since his basis in the property is your adjusted basis at the time of the gift.
You will just need to copy all your rental information reported up to the point of transferring the gift then remove the asset from your return so that your brother can report it on his return.
[edited 3/18/2018 - 6:05 PM PST]