This is always a difficult one, as many young men nowadays don´t wear watches or cufflings or gold chains, which used to be the traditional keepsake gifts for boys. I was surprised when my son (admittedly not 13 but in his late twenties), after my mother died was asked if he´d like anything from her house. He chose a brass Welsh miner´s lamp that my parents had bought as an antique many years ago and some small pictures they had on their wall. He now displays these in his flat, presumably to remind him of his grandparents. I honestly didn´t think he was that sentimental but am quite touched. How about a small painting, perhaps of a landscape or place that has a special meaning for both you and him?