I think the opening to Spy x Family fits the Bonebreaker family so well. After listening to the song(which basically describes the Forger Family) it kinda fits them too because they kind of mirror Loid, Anya and Yor(who are a spy, psychic and assassin). In this case the family consists of a Barbarian(Marrow's class), a Ranger/Hunter(Hamish) and Bard(Cole), and all have their secrets which they hide from each other, but theyre just as much as a real family just like Loid, Anya and Yor. The song reminds me of them so much.
as to what secrets the Bonebreaker family is hiding i'll avoid saying here because spoilers