Two things: groups are composed of individuals. Vice versa makes no logical sense.
And citing families and citizenship is a major stretch, given where the conversation started. I guess being an American citizen makes me part of a group, but that's not what Marty or myself were referring to, which would be better described as "sub-groups", which are created more to separate people than anything else.
I didn't chose my family, so I don't see it as a group akin to considering myself an Irish-American (I don't. I'm just an American). Where my ancestors lived means very little to who I am and how I live my life today.
The groups a person joins, be it voluntary or involuntary, very much shape and form the way a person thinks and acts. Therefore, an individual is composed of the groups he/she is a member of.
No, the group is composed of its members. The individuals are "influenced" or, possibly, "shaped" by what they have learned or experienced as a result of being members of those groups. Semantically, "composed of" is just not logical.
I learned a lot from my parents, my opinions are partially influenced by my time spent with them, but I am not my parents. I am very much an individual, separate from and different from them. I am not an amalgam of them other than genetically. I certainly don't contain all of the genetic data of everyone I went to high school with, nor was I particularly influenced by the majority of those people, since I didn't even know most of them.
Citizenship is even greater of an abstraction. I know maybe a hundred or so of the millions of US citizens out there, yet I'm composed of them all? That's nonsense. I'm thinking this would make sense to me if I were a big fan of collectivism, which I'm not.