Wait what ? I don't remember that kiss in both WN and LN.
After some serious incidents in the past, the aunt saw the mother doesn't have what it takes to protect and live with her son.
He didn't. He only cured the Seven Shades, his sister and 666. Alpha and Epsilon took care of the rest (and also recruited them, that's why Cid did not know Shadow Garden has that many members)
Nu is the first one that was not cured by Cid himself, but by the Seven Shades.