What is the order of preference among sisters for guardianship when direct ascendants are unavailable?
Chapter on Who is More Entitled to Child Custody
Al-Mughni
Book of Maintenance (Nafaqāt)
Primary text
When fathers and mothers, however high in lineage, are absent, guardianship transfers to the sisters. Sisters take precedence over other female relatives like aunts (paternal and maternal). Sisters are prioritized because they share in the lineage and are prioritized in inheritance. Among sisters, the full sister (both parents) is prioritized due to the strength of her kinship, followed by the paternal half-sister, and lastly the maternal half-sister. Ahmad explicitly stated this order, which aligns with the apparent view of the Shafi'i school. The justification for prioritizing the paternal half-sister over the maternal half-sister is her stronger position in inheritance, where she stands in place of the full sister when absent, and acts as a residuary heir ('asabah) with daughters.
Supporting text
Abu Hanifa and others maintain that the maternal half-sister is prioritized over the paternal half-sister because she relates through the mother, similar to how the maternal grandmother is preferred over the paternal grandmother. Ibn Surayj posits that the maternal aunt should be preferred over the paternal half-sister due to the maternal relation. However, the primary view asserts that the paternal half-sister's stronger standing in inheritance dictates her preference.