Festae are in the same tribe as a 'true parrot' (Hoplarchus psittacus). They are Heroines. But Acaras and saums , most definately not! Those belong to the tribe Cichasomatini. The group that aquarists generally refer to as Acaras.
A sev X con hybrid? I want to see real good eveidence of it, before i accept that it is possible.Though I have seen pics of a fish that was suposedely that, and did apear to pocess traits of both! Not so inconceivable that some kind of CA x sev cross is possible as they are part of the same tribe......but are distant enough to be considered to be of different clades with in the tribe Heroini. Eventually, probably just a matter of time before ichthyologists break up the tribe Heroini into more groupings. SA fish like sevs, discus, uaru, festivum,'trueparrots', chocalates, angelfish ect. are close to CA....but not that close.