How to legitimize this kid as my son? He's my lovers child and i'm sure he's mine

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https://preview.redd.it/rxnyqy4rhb3b1.png?width=1920&format=png&auto=webp&v=enabled&s=08455ac6858ca779784128374e22c0bbd8709ee0

His mother was my heir's wife, i seduced her and got an event where she was pregnant, the "a scandal awaits" one, and chose to reveal the secret to everyone since he's a genius, but i don't have a option to legitimize him or anything. Doesn't even say he's my kid