Most US citizens and permanent residents want to bring their close
family members to the country to live with them. However, this is not an
easy process and involves a lot of complications. A Green Card is a work and residence permit given to an individual living in US legally. A family based Green Card
is issued to an individual who is a relative of a Green Card holder or a
US citizen. So, only a permanent resident or US citizen can sponsor
his/her family member(s) get the residence and work permit in the US. Family immigration ins refers to the immigration of members of the family of a permanent resident or US citizen.
Source:
Know Everything About Family Based Green Card Process