Was there an ancient God in Egypt born on Dec. 25?

No. There's no scholarly support for such claims. I made it a point to read the Egyptian myth concerning Horus and there is nothing about Dec. 25 or 12 disciples. He was born after Isis had sex with Osiris' severed penis. No mention of when he was born nor of his having any disciples. It speaks of him going on to kill Set, his uncle, who killed his father Osiris.