If you breastfeed an infant for five times or more, the baby becomes a mahram for you and your husband. At that time, the status of the child is the same as your own biological child, i.e. does not void the ablution and does not have to cover awrah. According to a hadith:

"يحرم من الرضاع ما يحرم من النسب"

Which means: "What is forbidden by suckling or breastfeeding is the same as what is forbidden by lineage". (Narrated by Bukhari and Muslim)

However, a mother and her nursing child do not inherit from one another.