And, clearly, equally unoriginal parents.
Who also decided that exile and a life of grueling hardship was better than corrective surgery.
It's kind of dumber than that.
Triclops was made a slave because Palpatine viewed him as a failure and the Imperial leadership thought he was insane. He was unstable mind you, but not insane. His mother died in childbirth, so she couldn't do anything about it.
Trioculous was made in experiments on Force based creation run by Triclops' mother on the orders of Palpatine. He was the closest the project ever came to succeeding and the whole thing got scrapped and his biological mother and him were shipped off to the same slave mines as Triclops in a craaazy coincidence.
There he managed to get adopted by an Imperial because he was a brown nosing snitch on the other slaves and eventually became overseer, and delighted in torturing Triclops because he was actually Palpatine's kid while Trioculous was a failed lab experiment of his.
Part of the Imperial Remnant considered making Triclops the new Emperor, dismissed him as unsuitable and propped Trioculous up as a figurehead to take advantage of the rumours about Papa Palpatine having a three eyed mutant kid.
Triclops had a child with a 'jedi princess' or some such nonsense, they went on a few adventures and then disappeared to never darken the EU with their weird ass concept again.