I Have a Twin!? (Harry Potter and Percy Jackson) on Hold

I always thought I was the son of James and Lily Potter turns out instead of looking like my dad I looked like my brother. I always thought I was weird even for a demigod as I could do some random things when I was feeling strong emotions but I never imagined this. Harry Potter and Percy Jackson are twins but they never knew it their mother Sally is a witch and their father is a god. all wizards know about demigods and all demigods know about wizards but neither ever thought they could be both.
disclaimer I do not own any of the characters but I did come up with the storyline I know it is similar but due to the number of fanfics, it is not hard so sorry