Marco is viewed by this family as "fictive kin".
We can define fictive kin as the individuals who are viewed as being a piece of a family despite the fact that they are not related by either blood or marriage bonds. Fictive kinship may tie individuals together in ties of love, concern, commitment, and obligation.
The term Fictive kinship may likewise be utilized as a part of a legitimate sense, and this utilization proceeds in social orders where these classes and definitions with respect to family relationship and social ties have lawful cash; e.g. in issues of legacy.