Some additional or rephrased thoughts on kinship, now that I’m not working to a deadline, nor as tired.
Family of origin. There’s luck and privilege involved here, both in having a family of origin you want to have a relationship with, and that wants to have a relationship with you. When there’s choice about it, it’s most often only available to legal adults, at least when it comes to a relationship with one’s parents. I choose to have strong, central relationships with my family of origin, this is active work but work I can only do due to luck and privilege.
Family of choice. There’s some more freedom here, but not everyone goes into life or even into adulthood with the skills, time, energy, mindset etc to form strong bonds with unrelated people. I’ve reached 30 without really doing enough work here.
Children. In talking about the legal relationship, I’m assuming a fair bit more luck and privilege: that is, reproductive control. In that case, one is not legally required to have children in the same way that children must have parents/guardians. In either case, one’s relationship with one’s children is in an interesting place as something like family of origin (traditionally endorsed, legally recognised, tightly societally scripted) and like something else: a very intimate relationship with someone you don’t know at all and who will change quite a lot, very quickly. And in some circumstances, one can choose this relationship without any input from the other party (unlike being assigned your parents, in which one usually has no choice, or being assigned your siblings, in which neither sibling typically has any choice). It’s a very odd thing.
So for me my relationship with my child is somewhat outside the “family of origin”/”family of choice” narratives that I’d at least had a long time to consider. It’s not the only relationship one could have that has these features, but it’s the major one I’ve had, and I don’t know that I can write well about it until the story has played out more.
 Some luck and privilege here!