No need to be impressed. She suspected it from what little Riku would tell her, and how she felt drawn to him, as she was starting to feel from this other boy as well.
Namine laughed a little. That sounded more like something a four year old would do. "It feels familiar." She told him with all honesty. "You feel familiar." Because he was like Riku. Sometimes, she knew, she didn't much tell her two brothers from one another. "I know I can't offer any proof that I might be who you wish I am," Namine told him. She just couldn't, there was no way to tell. "But it would mean a lot to me, if you would accept me to be that sister." Her brothers were what she remembered the most, were closest to her heart of any family that was outside of Balamb.
SEE?! Sora was right to make Corin wait. He wrapped his arms around Riku tightly, this time his turn to rub his back gently. "You should not be afraid, Riku. He seemed very kind, and it seems he has carried the blame for losing his younger siblings all this time. He was very insistent to see you, and he had many questions, not all of which I answered."