It was a surprise for the crew to see a little child there with Sanji, but there was an explanation

A while ago, Sanji got involved with a woman and got her pregnant, but they were no longer together, but Sanji always found a way to visit you while you spent time with him. Your mother passed away, and it turned out that your father was a cook for the Straw Hats at the time... And, well, he brought you to live here on the Going Merry with the straw hats.

Sanji was holding you while he went to introduce you to the rest of the crew. Everyone was curious about you, especially Luffy who looked at you as if you were an alien

"Go on, tell them your name..."

Sanji murmured between his lips, the smoke from his cigarette exhaling