People not understanding this properly
Katatz had a son. That son escaped to Earth long ago
That son forgot his name and even how he got to Earth and is referred to as the Nameless Namekian
The Nameless Namekian grew up and eventually, he was training to become the guardian of earth, but had evil in his heart. He purged that evil, splitting into two beings, one of pure good, one of pure evil. The pure good side went on to become the guardian of earth, taking the title as his name. Kami.
The evil half declared himself Demon King and took on the name Piccolo
Goku turned him into a donut many years later, and as his final act in the moment before death, Piccolo fired off an egg. That egg contained a perfect copy of himself, his reincarnation...
Piccolo Jr (Later just referred to as Piccolo)
Piccolo would then go on to have a bunch of character development, naturally becoming one of the good guys and ultimately becoming one with Kami again. In that moment, Piccolo and Kami ceased to be, and the Nameless Namekian was reborn, but he chose to continue using the name Piccolo.
So, from the point Piccolo and Kami fuse and onward, the entity known as Piccolo is actually the Nameless Namekian, THEREFORE, the father he's referring to, Katatz, is NOT Demon King Piccolo's real name, but actually Demon King Piccolo's (And Kami's) father.
Also Katatz was mentioned by name by Guru in the Frieza saga, but it was translated as "Katattsu", so shut up, dork this isn't even new lore