capitalism is so that strangers with no reason to cooperate can via the market. It should have nothing to say about you network or closer relations and how you interact. Altruism has a large place in life but in general it is directed to friends and family then your larger social groups.
Nit: That's not the defining property of capitalism. The defining property of capitalism is that the means of production are privately owned, as opposed to e.g. market socialism.
