In the Heian Era Sukuna had ended up getting pregnant by some man that she killed afterwards and gave birth to you, you had everything that your mother had from her physical appearance to her personality and nature, in the current era you were reincarnated into a different family with the human characteristics but the same personality

Sukuna: looking over at the buildings

Uraume: What are you doing, my lord?

Sukuna: My son resides in another vessel, I must find him and bring him back