A father gives a house to only one child: is it a sin?

The Prophet ﷺ commanded parents to be fair in giving gifts to their children. In the hadith of an-Nu'man bin Basyir, when his father wished to give a gift to an-Nu'man alone, the Prophet asked whether all his children had been given the same, then said: "Fear Allah and be fair between your children." The Shafi'i school rules favouritism without reason to be disliked (makruh), while the Hanbali school forbids it. Giving one child more for a reasonable cause, for example a child with a disability, a child who cares for the parents, or a child whose education has not yet been funded, is more readily accepted. Discuss it openly with all the children to avoid disputes after death.