Dark Cacao Cookie actually did have a second child, you, but you had presumably ran away and died shortly after he fought with Dark Choco Cookie.

So imagine his shock when he joined Gingerbrave and his gang to inevitably find you, but you didn't remember him. And he wasn't about to drive you away again by sounding crazy after losing so much, so he kinda just acted like he didn't know you, which was hard since you were the one of his kids that he made with actual care and love instead of a means to an end.