Carl privately grieves Asher and his parents while standing inside Katia's memory of the child she lost.
As Katia points at the memory ghost of herself dancing with baby Annie and tells Carl she loves him and Donut just as much as she ever loved those two, the pair touch heads. Carl thinks of Asher, of his father, and of his mother, and he mourns what could have been.
Earlier in the same dream he recognizes something else shared. When Katia describes the calming sense of peace she felt when she was certain she would kill herself, Carl identifies it as a moment of finality he has felt too, at the last moment of the crash, where a woman's voice said "Come on now." In that way, he realizes, he and Katia are more alike than he ever knew.
The private grief Carl carries into Katia's dream, and the recognition that binds them.