In the days after the Battle of Hogwarts, the Golden Trio were asked to visit the families of those who died in the war. Harry made it a priority to visit as many as possible, accompanied by Ginny Weasley. Hermione had decided that the children who had lost family were her priority. She asked Viktor to go with her to see what could be done for the orphans.
Ron Weasley declined visiting the families because it interfered with his celebrity status.
The orphanage Viktor and Hermione visited first was in absolute chaos. No one knew how to deal with the influx of bewildered children. Hermione took charge and called in some help. Minerva McGonagall and Poppy Pomfrey came immediately to suss out the problems. Viktor was trying to calm some of the littlest ones by telling stories. A very small girl clung to him as if he was her only hope. Her crying tore at his heart. He looked around at the sheer numbers of orphans and made a decision. Sending a Patronus message to his parents in Bulgaria, he asked that they organise an international committee to find relatives of these children. His mother had done something similar when the Communists had fallen from power a few years before.
The sight of Viktor holding the tiny girl on his shoulder set Hermione's heart to thumping wildly. She saw the anguish in his eyes. Minerva told her that particular child was a Muggleborn and there were no living relatives to claim her. Hermione sent a Patronus message to Harry at Grimauld Place, asking if she and Viktor could bring a child with them. Harry replied that he and Ginny were at the Burrow and the house was theirs to use as they saw fit for the nonce.
She took Viktor's hand and Disapparated the three of them to Grimauld Place. The house was quiet now that the remnants of the Black family belongings had been removed. It was lighter and more home-like since Kreacher had changed the décor to a lighter motif.
The old house-elf met them at the door and immediately Transfigured a room into a child's room complete with toys and a bed.
Hermione took the sleeping child and bathed her before putting her to bed. A plethora of cuddly toys appeared in the cot around the child. Viktor watched silently from the doorway.
When Hermione was done, they walked down the stairs to the kitchen. Kreacher had fixed a late repast and brought out a bottle of the best elf-made wine.
"I know you want to take care of her, Viktor. It would be hard, what with Quidditch starting up again. Are you going to ask your mother to take care of her?"
"No, I want to keep her with me. Do you know what she said? She asked me if I was going to make the nightmares go away. How can I possibly go back to Quidditch after seeing the devastation these children have suffered? It tears my heart out, love. I want to take care of them all."
"There is another way, Viktor. If you had a wife… A wife could take care of her while you play Quidditch and the three of you could be together all the time."
Viktor looked at Hermione with so much love in his eyes that she blushed.
"Are you proposing to me, love? Seraphina needs a mother who would protect and love her. I know you are the kind of witch who loves unconditionally. Are you sure?"
"Oh, yes, I am very sure. You are the only man for me, Viktor. And Seraphina is the most adorable child. We can make her happy, I know it."
The next morning, Viktor, Hermione, and Seraphina went to the Ministry where Viktor applied for the marriage license and filled out the papers to adopt Seraphina. Kingsley Shacklebolt approved both requests personally.
By the end of the day, Viktor, Hermione and Seraphina were truly a family.
Hermione Diggory's prompt was: Viktor overhears a little girl's impassioned plea. Deeply touched, he sets out to make her wish come true.