One of the most famous but often surprising pieces of Moomin trivia is that Snufkin and Little My are siblings.
This fact is revealed in the novel where Little My is first introduces, Moominpappa’s Memoirs. The novel tells the story of Moominpappa and his group of friends in his youth, including Snufkin’s father Joxter. The novel includes a scene where Joxter meets happy and carefree Mymble, who Moominpappa confirms to be Snufkin’s mother. As Mymble gives birth to Little My during the events of the novel, Little My is either Snufkin’s older sister or older half-sister.
However, many people start out with Moomins through various adaptations. More often than not, this happens through the massively popular 1990s Japanese animated adaptation Tanoshii Mūmin Ikka / Moomin. This is why the above trivia can be surprising. Especially for fans with excellent memory, who have noted that Little My expresses romantic interest in Snufkin and in one scene, she even outright asks him to date her. With this, it is not uncommon for fans to make assumptions about the two characters now knowing they are siblings or even that the show is promoting incest.
There is a simple reason for this. Little My and Snufkin are not siblings in this adaptation. The most simple basis is that no animated adaptation of Moomins would purposefully promote such relationships and as this adaptation was produced with direct approvals from Jansson siblings, there are no accidental choices in the show. But further details below.
Moominpappa’s Memoirs was adapted for the show in three episodes that cover all major elements of the original novel. Snufkin’s father Joxter makes an appearance in the episodes as one of the main characters and he is confirmed to be Snufkin’s father here as well. Like in the novels, the company proceeds to a faraway land where they meet a young mymble. This is where the differense happens. In the novel, the girl they meet is called Mymble’s Daughter and will soon become the older sister of Little My.
The animated adaptation has changed this. In the Japanese version, the young mymble is simply addressed by Moominpappa as a girl who resembles Little My. In many other dubs, this young girl is introduced as Little My’s mother instead of her older sister. It is clear that this spunky little girl has very little in common with Little My’s elder sister as she appears in the adaptation, even though they are both named Mymble’s Daughter. But considering names in Moomin novels and this adaptation and the nature of this name, this is not surprising. This leads to the fact that this young mymble’s mother is no longer introduced as Little My’s mother and Joxter never expresses romantic feelings for her.
This is further cemented in another episode, where Little My’s mother and her multiple siblings were introduced. This woman had a very different character model than the older mymble who was that young girl’s mother, notably the ears. She is also a completely new acquaintance to Moominpappa and Moominmamma, instead of someone they would have known for years. Snufkin’s mother in the animated adaptation is unknown.
This change is actually something that Tove Jansson did herself as well. The above mentioned episode with Little My’s mother is based on a comic strip story that introduced Little My to Moomin family in that universe. Here Mymble is also a character completely unrelated to Moominpappa or his youth. Joxter is not mentioned in comics and Moominpappa never confirms if he knew Snufkin’s father in this version. Notably Sniff is no longer related to Moominpappa’s friend Muddler in the comics, so Snufkin’s relations might also be adapted out.
I hope this clears the issue even though the post is quite long. Relationships in Moomin books are very adjustable and Tove Jansson herself loved playing around with them, adapting them from novels to comics and even between novels as best suited the story. All adaptations are best treated as individual universes with only basic structures in common.