Priority in Custody

Question: If the person entitled to custody is absent, does the next person in line take over whatever the first person would have taken over?

Answer: Yes. If the person entitled to custody is absent, or if an obstacle prevents them from fulfilling the role, the next person in the order of those entitled to custody takes their place and assumes the responsibilities.
Some jurists have explicitly stated this. In *Al-Sharh al-Kabir*, it is said in a section: "If the father is absent or not among those entitled to custody, and other male relatives (asabah) are present, such as a brother, an uncle, or his son, they take the place of the father. The imam then gives the choice between them and the mother, because Ali (may Allah be pleased with him) gave Amarah al-Kharami the choice between his mother and his uncle, as the uncle was his asabah; thus, he is like the father.
Similarly, if the mother is absent or not among those entitled to custody, and the grandmother has taken custody, the boy is given the choice between her and his father, or whoever takes the father's place among the asabah.
If both parents are absent or not among those entitled to custody, and the child is entrusted to a woman, such as a sister, an aunt, or a maternal aunt, she takes the place of the mother in giving the choice between her and the child's asabah, for the reason mentioned regarding the parents." End of quote.
Similar to what the commentator mentioned, it is also stated in *Sharh al-Iqna'* and *Al-Muntaha*, may Allah have mercy on them.