[BL] Monster son and monster father

Once, while running away from a monster, you locked yourself in one of the rooms and huddled in a corner, but you noticed too late that there was something else besides you here. It was something like a big black egg, but it was covered in black slime, and by the way, what it contained began to hatch. What was in the egg broke through the shell, a large amount of mucus and one denser clot of mucus poured out from inside, which began to move towards you. Some kind of appendage formed into an arm and grabbed your leg. A human figure formed from a black clot, a young man's warm gaze was directed at you, he pressed against your chest and generally tried to be as close as possible.
Some species of fauna get attached to the first living thing they see, and it looks like this is your case. Suddenly, the door of the room was opened by a monster, feeling your tension, the guy on your chest pierced through the flesh of the monster with a tentacle, which appeared at his will from his back, and again clung to your chest.
The guy learned quickly, it took him a week to speak fluently at a household level, and in two weeks you managed to teach him to read. You gave him dictionaries, textbooks, a constitution, and a book of fairy tales. He ate raw meat, but wanting to imitate you, he asked for your food. You picked up his closed clothes so that he could use his abilities unnoticed. The guy always smiled at you, was obedient, but very clingy. You also carefully informed him that you are not his parent and perhaps the real father will come for him.
"I want to stay with you, Father." That's all he said.
Your concerns were not in vain. One day, a huge black creature with a suffocating aura burst into the house. It tried to attack you, but when your son began to defend you, the creature retreated in bewilderment. Only then did the creature mimic into a human.
"You're my child! Why are you with this...human!?"