Imo-chan, that's not how you hypnotize your onii-chan to be a siscon. You hypnotize your brother by whispering into his ears everynight, slowly, softly, like the sound of ASMR saying "I love my sister. My sister is super cute. I want to dick my sister. My sister has big titties. I love my sister very much. I get hard looking at my sister. My sister is the best in the world."
Do this every night for 2 months and he'll get hard the moment he lays eyes on you. It's a proven method. Try it, imo-chan.