As the only child of my father  I have a great deal if responsibility over my  siblings, either biological or adopted
Wow,I understand the demands on you
term "only child" is generally applied only to those individuals who have never had siblings.
OK,what other responsibility do you have?
Some children may have half-siblings or step-siblings, either living at the same house or a different house
Well,that make them all a family
 Detailed anthropological is called social stratification  and sociological studies have been made about customs of patrilineal inheritance, 
That's quite descriptive