Well, yes, liberalism is often pushing against building a society where we have "clans" or "groups" that exert authorities on individual actions.

I don't think it means that "ideas like the nuclear family are hard to define within liberalism". I think they define them as clearly as in conservative circles (if not better, in conservative circles, these notions are often "gut feelings").

And I don't think liberalism is trying to ban things like nuclear family. People can still have as much nuclear family as they want, as long as it does not impact people who don't recognise their arbitrary authority or who are not part of one (willingly or not).

For example, Black Lives Matter is a good example, as they never rejected the nuclear family itself, just said they don't recognize its authority when this structure is restricting the solidarity potential between individuals.

Same with citizenship: it is not true that liberalism struggles with this notion. Liberalism is just trying to find a fair balance and avoid cases of unfair restrictions on people whose only crime was to be born on the wrong side of an imaginary line. It does not mean citizenship is rejected in itself, but it means that you cannot arbitrarily invent rules that favourise the group you are part of.