i have had 2 types of boar pairings that have worked well,
2 piggies that were both 3 months old
2 piggies one was 5 weeks and the other 3 months
i haven't come across any much older boars as of yet all mine are under a year, but i would say of course age is an issue but i find the most important part is to make sure there personalitys are compatible for example i have a pair that are both submissive,(great friends but the best pair is) Smokey and Bandit,Smokey is a very dominant/grumpy piggy but Bandit is submissive and playful so he evens out smokey perfectly,i would say most personality pairings go well except 2 dominant piggies because then there is almost always a fight,with a 2 year old i'd recommend a piggy up to 6 months old that is your safest bet xxxxxxx