remember that in case of adopting a girl, Raḍā’at[1] will be established with the husband, i.e. the husband’s sister or niece will breastfeed the girl. In case of adopting a boy, Raḍā’at will be established with the wife, i.e. the wife herself, or her sister, daughter, or niece will breastfeed the boy. If this is done, then there will be no veil restrictions for both the husband and the wife.
Remember that whenever you wish to establish a relationship via Raḍā’at, then breastfeed the child within the age of two years (according to Islamic years). It is not permissible to breastfeed a child after he has reached the age of two years, even for a mother to breastfeed her own child past the age of two years is prohibited, but even if a boy drinks a woman’s milk within the first two and a half years then a relationship through suckling will be established.
Question: When does a boy reach puberty?
Answer: Between the age of 12 and 15 (according to the Islamic calendar) whenever a boy ejaculates (whether through sexual intercourse or masturbation etc.) or experiences nocturnal emission or makes a woman pregnant he will have instantly reached puberty and it will become Farḍ for him to perform Ghusl. If any of these do not happen, then he will reach puberty as soon as he reaches the age of 15 according to the Islamic calendar.
(Durr-e-Mukhtār, vol. 9, pp. 259 – summarized)
Question: When does a girl reach puberty?
[1] Raḍā’at implies relationship formed on the basis of breastfeeding a baby under certain conditions. See its details in Baĥār-e-Sharī’at.