Double Header (LSH TV series); Double-Header (Earth Zero) {Note: this version of the character was referred to in Action Comics vol 1 #860 (Feb 2008) as having been killed, but was never seen]
Frenk and Dyvud Retzun, alias Double-Header, were from Janus, a world where a species starts as conjoined twins and eventually split into two identical beings. Whilst this is an interesting biological process, it isn't exactly an impressive power.
The Janusians were revealed to have been a group of genetically-engineered humanoids who were part of a eugenics program to create superpowered beings undertaken by a species called the Dominators. Lar Gand rescued the test subjects and relocated them to new lives on other worlds. Those with the same power as Double-Header were placed on Janus and made it their home.
The pair combined were excellent fighters, but Frenk and Dyvud's constant bickering led to their rejection by the Legion. The pair joined the Legion of Substitute Heroes Auxiliary (as the Subs did not like to reject anyone completely) but failed to do anything remotely useful.
