Answer: Fictive kin
Step-by-step explanation:
Fictive kin is the person who is considered close and significant as a family member even though they are not related with the person from time of birth or through marriage. Family-like relationship is created with these people to support person socially, provides community sense etc.
According to the question,Marge is fictive kin for the person.As Marge provides closeness and support to the person like a family even though she is not related to him .The person welcomes her at family occasion and seeks for help and support from her in required situation.