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After their mother's suicide, 14-year-old gifted Siméon, 8-year-old Morgane and 5-year-old Venise Morlevent swear never to be separated. Custody is contested between their frivolous, gay 26-year-old half-brother Bart and their respectable married half-sister Josiane, who wants to take the youngest.
The person best suited to raise children is not always the one with the most stable life or the most conventional profile. Fitness to care is built by repeatedly showing up for concrete tasks such as hospital visits, school runs and nightmares, and the commitment follows from that work rather than coming before it. The immature adult becomes responsible because the children's needs keep demanding it.
Judges and social services tend to measure fitness by visible markers such as marriage, income, orderly homes and sexual conformity. These proxies can favor a guardian who would break up a sibling group over one the children actually trust. Asking whom the children are attached to, and what keeps them together, exposes bias hidden inside apparently neutral assessments.
Children facing loss create their own rules to protect themselves, such as a sworn oath never to be separated. Adults then have to negotiate with that pact instead of simply overriding it. The siblings' insistence on staying together works as a demand that shapes every adult decision about their future, and it shows children acting on their own behalf rather than as passive objects of placement.