Does Islamic law and civil law permit separating siblings from the same father in upbringing? And what are the circumstances that allow for the custody and upbringing of all children together?

The gathering of siblings from the same father for upbringing and custody is not obligatory, especially when the spouses separate; because the mother has the right to custody of her children, based on the Prophet's (peace be upon him) saying to the woman whose husband divorced her: "You have more right to him as long as you do not marry." The father's right to visitation and discipline is not forfeited. If the legal conditions for a custodian are met by the father, and there is no one more entitled to the custody of his deceased wife's daughters, such as their mother, then he has the right to their custody. However, after the mother's death, the majority of jurists hold that custody is established for the maternal grandmother, contrary to a narration from Imam Ahmad that the father has more right to the custody of his children after the mother's death. When there is disagreement regarding matters of custody, one must refer to the Sharia judge.