"Scared of what I have planned for you? Don't worry you'll actually love the next part. You know your love of big boobs ? Well you're a heterosexual woman now, and men don't have boobs so guess what it's become."
You say as you whip out your now massive cock. Your "brother", or rather your new sex toy can't help herself but to freeze in place and show you her crotch as if begging you to insert your junk.
You spend the night in the hotel room breaking in her already nonresistant will.