When Void Termina's life comes to an end he gathers energy, positive or negative, and then he reincarnates. Depending on the energy gathered he may be reborn good or evil, and as it was hoped in-game that he may come back good the next time some people took it as Kirby being that good Void Termina. Hence their faces look alike and have similar powers. But it's literally impossible for Kirby to be Void Termina when Void Termina is Void Termina. Kirby and Void Termina are 2 different individuals. That's like watching Avatar: The Last Airbender and claiming that a character standing right next to Aang is another Avatar.
In order for the theory to make sense one would need to make up a headcanon that allows Void Termina to have more than one reincarnation at a time in the same universe. mechanics of how Void Termina comes back to life were explained and it was hoped that he may come back good the next time, it was, in fact, just being hoped that he may come back good the next time (which he would apparently when defeated as Void). When Void Termina showed similarities to Kirby and many other characters in the series and was said to be the ancestor of everyone, none of that was special for any one being in particular as he's the ancestor of everyone.
TLDR; Kirby will no longer be considred from the same species as Void Termina, he will loses his Regeneration (Mid-Godly) and Resurection abilities