Justice League #24 makes it painfully clear that Ultraman's parents are evil versions of Jor-El (Jor-Il in Earth-3) and Lara.
Lara: This is all your fault, Jor-Il.
Jor-Il: Just shut up and die, Lara.
- Much later, we see infant Kal-Il crash land near Johnny and Martha Kent's home, here as two petty criminals and drug addicts. The first thing Kal-Il does is vaporize Johnny's hand with his heat vision and then clearly state "You two. You will be my parents now." Ultraman mentions he killed them when he was seven and razed the farm to the ground.