Thread:KinHikari/@comment-26359041-20200215000449/@comment-4039124-20200215165205

Tinomartino wrote: https://phineasandferb.fandom.com/wiki/Vanessa_Doofenshmirtz

I'm afraid someone wanted to make a joke on this page. The existence of a half brother of Vanessa has never been mentioned anywhere!

It's a possibility Derek could be a fanon character. Likewise with an "aunt" (Cricket) and a "great-uncle" (Harrison). Unfortunately, I'm not sure who added them to the infobox.