Does the adopted son inherit from the father who adopted him? And what should he do about the woman who raised him and breastfed him, and their relatives, given that he is unable to be independent due to his illness?

For a child to be registered under the name of their true father is a religiously required matter, as indicated by the verse: ﴿Call them by [the names of] their fathers; it is more just in the sight of Allah.﴾ (Al-Ahzab: 5). Adopting a child and showing kindness to them is a praiseworthy act, encompassed by the encouragement to sponsor orphans. However, it does not entail the effects of sonship such as inheritance, financial support, or the prohibition of marriage, for Allah Almighty says: ﴿Nor has He made your adopted sons your [true] sons. That is [merely] your saying by your mouths.﴾ (Al-Ahzab: 4). If the woman's sister nurses the child five known feedings, she becomes his foster mother, and her sisters become his maternal foster aunts, and they become unlawful for him [to marry], due to the Prophet's (peace be upon him) saying: "What is unlawful by lineage is unlawful by fosterage." He is permitted to sit with them and shake their hands. As for the sisters of the man who adopted him, they are not his paternal aunts, and there is no prohibitory relationship between him and them; he should treat them as non-mahram women. Similarly, the daughters of these women are non-mahram to him, except for the daughters of the woman who nursed him, for they are his foster sisters. Being kind to the child and taking care of him is a good deed, and Allah loves those who do good.