the poem 'A Photograph' is placed after the 'Portrait of a Lady' because of the thematic relation between the two. What is the relation?

The relation is that in portrait of lady explain about the grandmother loves ,care and all time Care but in A Photograph the narrator want that love ,and care that she not gain

In the first, namely the photograph the poet speaks about her mother and says that she misses her and her smile. She sees her photograph and realises that she has lost a great valueable thing in her life. Thus she feels lonely.
On the other hand, in the potrait of a lady the narator speaks about his grandmother who used to be a part of his life when he was a child. Now when he has grown up maybe he doesnt require her much but when she died he realises what he has lost.
Therefore the link between the two chapters is that both have the part of realisation of the value of a thing once lost. This says us that we human beings arent usualy able to value things we have but do understand the value of things we have lost or we dont have.

The porait of a lady shows beauty, eternal beauty of author's grandmother whereas in the poem The Photograph the beauty of author's mother had shown ,she enjoyed her chidhood . But as the fact both the story and poem tell us about death pf their loving one's.

 Khushwant Singh draws a pen picture of his grand mother. He describes how he had spent his childhood with her in the village. He also describes the change that came in the relationship in the city. Ultimately, he describes the moving scene of her death.