Is it normal to be young and feel so old

I am visiting my only family other than my parents over Christmas and I feel like the time is going so quick. My mum moved away from them when she was 18 and went to a different country half way across the world to be with my dad and recently I have been feeling so bored and lonely. I haven’t been having a great time with my friends, I had a best friend for 10 years and now as we get older we have stayed close but now as close as I would imagine. She has kind of moved on and seems to be forgetting me. She has a boyfriend that she always comes to me complaining about, saying that he is commenting bad things about her and being rude to her and I know that he is not good for her. But I just feel like I don’t fit in at school and among my friends but when I came over here for Christmas and I spent 1 week now with my cousins I have felt right at home and had endless fun. I say that to my mum and she always disagrees with me saying she doesn’t think her family likes her too much and she feels homesick and wants to leave. I only have 3 days left here and I want to suck up every last bit of it before I have to leave back to my boring life. I feel like it will be a long time before I will be able to come back to see my family and I am going to miss so much, I desperately want to get to know my cousins more than I do as we all get along so well but I don’t know how. My favourite thing about being with my family is that I can do things that my friends at home would never do. Like playing competitive sports. I have always loved that but the sports I love, they don’t have at home and my friends are not the kind of people to do that.

I may sound like I’m worrying too much or I’m not looking at it the right way, but I have no one to talk to about this kind of thing and I love hearing people advice because it really helps.