Oh no, that is not ok. For the safety of you, your family, and the child, your name, address, and phone number needs to be kept 100% confidential. If the childs family member is given your phone number, then they can easily find out your address. If this child was taken from the home by force, what's to say that family member won't show up, and kidnap the child! You need to contact your Child Protective Services Department, and ask to speak to your social workers superior, as soon as possible. Stay safe, and good luck.
Uhh, I have friends who are foster parents and they were kept absolutely 100% anonymous to the child's family. I was always under the understanding that the child's case worker or a representative would deal with the biological family... there's no reason for them to contact you, especially if it's a situation where the child was seized, as opposed to emergency support.
You really need to contact the local gov't agency and ask for your caseworker's superior to discuss this.
You should be confidential unless you authorized prior that parents can contact you. Some parents have an arrangement with the foster parents. If you are uncomfortable tell the parent you don't want them calling or change your number.