I don't even really watch this family (have seen them a couple of times) and am only reading this thread due to WFH boredom but your message really spoke to me. I didn't move as a kid but was very very wrapped in cotton wool by my parents and as such experienced very little, if any, social life outside of school growing up. I completely get your birthday party comment, too - I now socialise in an externally "normal" way most of the time but take myself on holiday over my birthday every year so as to avoid that horrible feeling of being rejected on my birthday.Longtime lurker here, but I can give a lot of insight into moving countries as I moved countries 7 times by the time I turned 16, and although I went to school in each country, I only stayed in a school for two years maximum and even then, I struggled socially and emotionally since I barely had any friends throughout my childhood, it got to the point where it was incredibly detrimental to my mental health that I developed a personality disorder. It took me until I was 20, nearly 21, that I was able to function a lot more socially and emotionally at the level my peers are at now, but I will never forget watching movies where the main character had a friend or even a group of friends and it really broke me down because I realized I had no one. Even now, I really wish I had normal teenage experiences (Halloween parties and NYE parties) and I am resentful of my parents for putting me through my childhood. I am incredibly terrified to have a birthday party with my friends because I'm still scared I have nobody.
I can't imagine what this is doing to Mia and Sienna and how this is all going to turn out, but I know eventually they'll suffer once they become adults and they will be so far behind their peers that they probably won't have many friends their own age.
Soz everyone else for going off topic but please message me if you ever want to chat x