Family members who may receive immigration benefits include, spouses, children under 21, and unmarried sons and daughters (children over 21) of US citizens and Permanent Resident Aliens, plus if the petitioner is a US citizen, married sons and daughters and their families, siblings (brothers and sisters) and their family, and parents, both mother and father. Both permanent resident aliens and citizens may petition for spouses and unmarried children, but only citizens may petition for married children, siblings, and parents.