Questions for Particularists

I am an American with two sisters. Suppose that, for whatever reason, one is a French citizen and one is an American citizen. Do I weigh my American sister's interests more highly, in virtue of our shared citizenship? (Start from an egalitarian baseline, then give both a bonus for being my sister, and then give one a bonus for being a co-national?) Or do family relationships trump political relationships, so I must treat them equally, as sisters. What if our countries are at war?
If you think it is permissible to weigh the interests of countrymen more highly that of foreigners, and it is permissible to weigh the interests your family more highly than your non-family, is nepotism permissible? To be encouraged? If you're a congressman and land a sweetheart government contract for you incompetent criminal brother, does that make you a bad American but a good brother? If you had to choose, which is it better to be?
You are the star quarterback of your high school football team. The state championship game is this evening, and your team cannot win without your gridiron virtuosity.  But you discover your twin brother, who was adopted by another family and whom you have never met, is in jail, and in danger. You can go bail him out and save him from being imminently beaten in jail by a gang he has crossed, or make the big game and give your team (which contains your best friends) a shot at the championship, but not both. What do you do? What if you were raised together and joined at the hip until he got mixed up in a bad crowd? But you're not genetically related? What if he is a French citizen? What if you have another brother on the football team? A cousin?
You are American. I have joined the French Foreign Legion and renounced my American citizenship. I have (a) betrayed you, (b) erased our prior mutual obligations as citizens, (c) both. Now, imagine you are French.
You are a Delaware patriot. Some guys from your state, who you certainly never got the chance to vote for, votes to incorporate Delaware into the United States of America. Do you now owe additional regard to the interests of Pennsylvanians? Suppose you did vote for your “representatives”? What then? Suppose you are an American patriot. A constitutional amendment is passed incorporating the United States of America into the North American Union. Do you now owe additional regard to the interests of Mexicans?
Three people are drowning in a pool and you can save just one. One is a fellow American. One is a fellow devout Catholic. One is your son's French atheist girlfriend. Is it permissible for any of these attributes to play a role in deliberation over who will save and who you will let drown? If so, which? If more than one, which weighs most heavily, and why?
I ask because I cannot fathom a set of general principles that could possibly govern these cases. Which leads me to suspect that those who endorse the moral centrality of duties based in egocentric attachment generally have no argument, rational or moralagainst policies that seem to them to run afoul of their imagined special affiliative duties, but are merely asserting an unwillingness to accept them. This amounts to little more than an affirmation of one's prior commitments.
A principled particularist would give us something like a complete schedule of prices: how many countrymen one brother is worth; how many Frenchmen one countryman is worth; etc. We'd then know, say,  how serious a transgression must be before breaking the “thin blue line” and ratting out a fellow cop, and just how many hours one is obliged to spend with one's “bros” relative to one's new girlfriend. We could then know how much immigrants must benefit to offset costs to natives, and thus what an acceptable (to the principled particularist) level of increase in immigration would be. However, a principled particularist is something like a contradiction. I suspect I will be told that these things can't be measured in terms of one another with any precision. So all we can know for sure is that candidate duties to others we do not presently recognize cannot really be our duties, since they are not rooted in attachments we already take ourselves to have, and may even conflict with ones many of us are sure we do have. The easiest way to adjudicate the possible conflict is simply to ignore the possibility of new duties it would be inconvenient to have. And, thus, everything is left as it is.