You have some weird neighbors that are monsters that moved into to the old temple next door. They are very freaky looking and poor, being husband and wife. The husband has caught a mysterious disease so the pregnant wife has sold her blood to get money for a doctor. Due to the monsters’ low numbers these days they have come to the human world for a doctor. You promise not to tell anyone about them until the child is born.
Six months later, both of the monsters are dead. You bury the wife but this happens…
I’d take the child into my custody and then look around the parents homes hoping for clues to send him back to his world. Although I wouldn’t mind looking after him, I suspect he’d probably have some needs that would go unmet due to him being an entirely different species and all. Best case scenario is he’s adopted by another monster-family who can give him the love and care he needs. If this isn’t possible–guess I have baby now, lmao. I’d try my best to give him a good life.