All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
According to the view of the majority of the scholars it is not an obligation on either would-be spouse to inform the other about him/her being sterile even if this is definite, let alone if this is not definite and it is possible for him/her to be treated.
The deficiencies that a man who proposes to marry a woman is obliged to inform her are the deficiencies that prevent sexual intercourse or the repulsive or contagious diseases such as leprosy, vitiligo and the like. For more benefit, please refer to Fataawa 90593 and 128182.
Based on what we mentioned that it is not an obligation to inform about fertility problems, then not informing about it is not considered as cheating, so this boy and his parents are not sinful for this, even though it was more appropriate to inform about it.
However, this wife is permitted to ask her husband for divorce due to the harm that is caused to her because of his sterility if she has despaired of him being able to have children while she wants children, especially that some scholars are of the view that sterility is a deficiency because a deficiency is anything that prevents an objective of marriage from being achieved, and among the most important objectives of marriage is having children.
As regards adoption, it is forbidden and this is discussed with evidence in Fatwa 82371. Therefore, it is not permissible for them to resort to it. Nonetheless, the door to do good to people is open and it is an act by which one gets closer to Allaah. So, they may nurture a child and be kind to him/her without adopting him/her.
Allaah Knows best.