Well, you may or may not know that I have Aspergers syndrome, and that I hate socialising. For christmas, my family will be hosting (again), so alot of my cousins, granparents etc. wipl be coming over, so I will unfortunatley, end up having to socialise with people. What's worse is that they're people I really don't want to talk to, so I was wondering if you have any tips to avoid conversation with grandparents and cousins over christmas.
Getting "sick" or getting a job, as mentioned above, are good options. I'd add, you could just, you know, not talk to them. If they keep pushing, keep the answers short, nod a little, shrug here and there. One of two things will happen, if you do this. Either your socializing company will stop, realizing you aren't providing much conversation, or they'll get upset -- which can work to your advantage. Nobody [in their right mind] likes unnecessary upsets, especially at family gatherings, so, you'll walk away scotch free. Basically, show no interest, keep it to a bare minimum with responses: subtle nods, lot of "... yeah..."'s. Most likely, this'll provide you with the detour, that you seek. There is another alternative, but it's not exactly friendly. But it works, if you require absolute avoidance of any and all socialization.
Help in the kitchen/cleaning up? Watch the little kids? Walk the dog? Some chore-like activity that keeps you too busy to sit and chat.
Never take your headphones/earbuds off. Every time someone addresses you ask them to repeat what they said one more time (even if you heard them) after removing just one of your earbuds (hold it in your hand [very important]). As soon as they are done speaking and/or you have answered their question put your earbud back on and resume whatever you were doing before giving them time to point out something else. Don't smile much, if at all. Don't frown either, the trick is to not look "inviting" or "approachable" without being hostile. Follow this to a T and in most cases they will subconsciously pick on your cues and take a hint.
To be honest with you, I think it will be hard to avoid conversation with family over the Christmas period without upsetting your parents/guardians and then you ending up having even more conversations and aggravation because you tried to avoid it in the first place. I know this because I, in the past, have tried to ignore family in certain ways and it always ends up making things more complicated and tiresome. It might be different for you but I'm not sure. Good luck anyway. If you end up being successful I could use some advice on how you managed to pull it off.
Do housework. Do things like laundry, vacuuming, cleaning your room or even the dishes. You won't have to socialize much and no one will question it either. They'll simply see it as being polite.
If you are not afraid of being rude... Interrupt them, by raising your hand, then simply walk past them, without saying anything. This will pretty clearly get the point across. Otherwise, as suggested, find something to do outside the house or... earbuds.