Currently on my sidebar over at Quillette: "The Great Scattering:" How Identity Panic Took Root in the Void Once Occupied By Family Life. It is more than just a discussion fatherlessness, though that is prominent. The idea that taking one's identity from one's group(s) would grow as the family, both nuclear and extended, weakened makes some obvious sense. We will draw an identity from somewhere. Making one from nothing is impossible, and making it only from oneself is difficult. Even individualists assemble their identity from things they find lying around. They provide shortcuts, good and bad - that is, they provide both inspirations and excuses.
There is a difference between saying "I'm Irish" and saying "My family is/was Irish," though any of us might say both at different times and mean nearly the same thing by the statement. The two statements give a different picture. I am going to bet that the latter formulation is much less common now than it was when I was a child.
I was a child of divorce (6), then remarriage (13), and those did not merely deprive me of some opportunities for identity, those events were part of my identity, which is a bit sad. In addition to obvious (though disquieting) sentiments of feeling as if one had two families or acted like a different person with each parent, the article quotes “I always felt like an adult, even when I was a little kid” as a statement children of divorce strongly agreed with more often. I nodded wryly. I had thought it was only me.
Each successive generation recently has fewer siblings, which means fewer aunts and uncles, and greater mobility also means less contact with extended family. That last is more variable, as Americans have been moving away from families for a long time, and communication with them has become easier recently. Yet the trend toward less extended family seems clear. (Though come to think of it, I don't know what the trend is among those who have immigrated in the last few decades.) Larger extended families have more group identity, and it is easier to find a place for yourself even if you don't like everyone. If you have an aunt that shares a passion of yours, that is more than having a random woman from the previous generation with same.
We will make an identity out of something. It starts early and we can't postpone it and say "I'll just put together a personality someday when I have time." When one large storehouse is removed, we will go to other storehouses for food.