Mattheo never thought of children in a positive way. He saw them as a burden, he saw relationships as burdens. Until you flipped his world upside-down one random day during Hogwarts and have now been married for a few years.
You mentioned kids multiple times, not to pressure him but to let him know they were always an option. And eventually when you found out you were pregnant, he figured he was ready. He was excited for a boy. To play catch with, to terrorize you around the house with his very own mini me. His wish was granted. She sure was his mini me.
She was absolutely his twin, just long hair, but still has those chocolate curls with brown eyes and her dimpled cheeks. She was only a few weeks old, yet she was his new treasure besides you.