Question

Why does ' smile through their hair mean?

Answer 1

the meaning is that in the photograph mother of the poetess and her cousins were smiling looking towards the camera man standing on the beach with there beach dressup and while smiling wind was blowing thats why their hair were coming infront of there smiling face and flowing in the direction of wind.

Answer 2

ANSWER :

This phrase is taken from the chapter  "The Photograph".

In the poem, it is mentioned that there was a photograph where the poetess' mother and her cousins were smiling while her uncle clicked the photograph. They were looking at the camera with happy faces to keep the photo as a memory.

So while their were ready to be clicked, wind blew across the beach which made their hair come infront of their smiling faces. This is the proper explaination of the given phrase.