Partridge doesn't say anything at first. Maybe he's flooded with memories, too, or he's wondering if he should invent some story for her, the way her grandfather did. Doesn't he want to be able to fill in her lost childhood, like a real brother could? (39.31)
Memory is highly individual; you can't have someone "fix" your memory. The best we can do as is try to remind someone of certain experiences… but if they can't remember, then sometimes the memory is just lost.