Alaska is adopted, there farther was originally Russia. Basically what happened is Russia couldn't handle being a farther after Alaska's (accidental) mother died. Russia and there mother never meant to have a child and months after Alaska was born there mother died. After a month of trying to figure out who could adopt Alaska and the only two other countries he asked to adopt them declining he turned to America. Ame at first didn't want to but ended up excepting.
Soon Alaska found out who there real farther, alaska always tried to talk to russia when they were little and now understood why Russia always seemed so uncomfortable. Soon russia warmed up to Alaska but always didn't feel totally comfortable around them and there still pretty distant.
No one exactly knows who alaskas mother was and ame didn't bother to ask since it was a secret relationship but it might have been the arctic
(Arctic and Russia are not related, idk why I had to say that they just seem like the typa guys that would be related in most au's-)
Since they died a while before this.
Alaska is also lesbian

NATO is a pretty interesting character, they have generalised anxiety disorder and anorexia nervosa.
As a child they were found by America as well as un of the street, when nato was 3 and un was 4.
NATO warmed up to America very quickly and became slightly clingy since for a lot of there lives America was the only person they ever had along with Alaska a few times.
NATO and un were very close from the start but as they got older became more separated as they got new priorities, especially when they turned into teens. NATO got more interested in athletics and the sea while un was focused on books about history and people motivations for certain actions like murder, violence or aggression as well as gaining a friend group.
When nato was 11 though they were up late and saw America coming in with loads of wounds on his body and America had to tell him the truth of what it's actually like to be a countryhuman.
NATO ever since learning this became extremely distressed and anxious, un soon took notice to this and tried to help nato but nato slowly started to become less trusting of others through time.
They are also demiromantic/bisexual

Un is also a character I really love. When they were a small child they were very protective of nato and untrusting towards America but slowly trusted him more.
Un researched a lot about people's motivations for murder or in general vile acts due to not understanding why anyone would do that. The more they read the more knowing but also confused they got. Un always cared for others and they cared for nato deeply but never quite knew how to express it. They do normally have a rude tone but they do genuinely care for others and want to take care of them.
Un through time slowly did learn how to express there feelings to others but when they were young they accidentally hurt nato more when he was trying to support them.
Un still does have trouble expressing his feelings and has diaries to write down how he feels or after an interaction he might regret he has trouble saying how he feels and normally uses notes to say how he's sorry but sometimes he is able to confront others.
Un is also eroace, he doesn't really want a relationship with others and it pretty weirded out by romantic advances.
If your not picking up the fact un is meant to be autistic here idk what will