The mystery of Ferb's bio-bro is a two-part comic/fanfiction story based on Ferb Fletcher finally meeting his long lost brother after almost a decade of his absence in his life. The trouble is, Terrance Fletcher AKA Zacros Xalon is not exactly a good brother to have... The story consists of two seperate parts, the first one being 'Secret sibling shenanigans' and the second one being 'The shocking truth' and they fit together via immediate continuity.