Is a legally adopted sibling considered equal to birth sibling in a deceased persons estate

If the decedent, an ancestor of the decedent, or a child or other descendant of the decedent legally adopted the person in question, then yes, that person would be treated the same as the biological relatives for purposes of determining the heirs to an intestate estate (who are also the persons given the chance to challenge a Will). Whether a person adopted into a family would be treated the same as biological relatives under a Will actually will depend on the provisions of the Will itself- state law considers adopted relatives the same as blood relatives, but some Wills do not treat them the same way. However, if the person was adopted OUT of the decedent's family, for example, if the person is a biological sibling of the deceased person, but was given up for adoption and legally adopted by another family, then that person is NOT normally considered a relative of the decedent for purposes of Georgia law.