Back up a little, and clone a twin

Looking back on her childhood, Hermione regrets being an only child. She had few friends growing up due to her passion for reading obscure and overly advanced textbooks, and neglecting to hang out with other kids her age. It’s not like she could do anything about that fact, except that now she can.

Hermione twists the Time Turner thrice more, and arrives just a few minutes before her own birth. She quickly casts a charm to make her presence unintrusive, before her anxious parents and the doctors become alarmed by her sudden appearance. She looks lovingly at her younger mother, and the swollen belly that must contain her unborn self. She wastes no time in raising her wand again, and casting a spell, “Corpus Iterum.”

Her mother, already panting from being so close to delivery, let’s put a weak bowl as the baby inside her bulges to nearly twice her original size, stretching her womb unexpectedly as Hermione’s father watches on in awe and horror. Baby Hermione then liquifies, before immediately reforming into two identical copies inside the womb, now both her original size. Hermione’s mother wheezes from the abrupt changes, though none but Hermione is aware of what has truly just happened.