As wiebke said i have 13 boars and havent had to many major issues my pairings are as follows
Smokey-10 months paired with Bandit-10 months
Basil-6/7 months paired with Ralph-5 months
Zanzabar-10 months paired with Baker-13/14 months
Cooper-8/9 months paired with Windsor-3/4 months
My trio Uncle Prescott-12-18 months and his nephews Panda and prince who are around 12 months old.
And then i have Blade & Rajah who were paired but fell out after a long ride home in the carrier from the rescue(they werent stable at the time anyway) and since i have tried to get them back together and it just wont work so now Rajah is getting Bonded in with Basil and Ralph and Blade(the difficult one) will be getting a baby boar.
So as you can see i have lots of ages most of them are in testoserone overload and are still getting along fine,i think there are a few key thibgs to a good match i usually prefer a submissive pig paire with a dominant one or a baby to an adult,you are taking one of the safest ways possible to bond boys so i wouldnt worry to much,many people hear all sorts of bad things about boys that just isnt true even adults can be bonded with eachother,my reserved boys at rescue have never been together they are 8-10 months and 1-2 years of age and they have been successfully paired with ease,
Of course nothing is guaranteed but its not as common as some think.
I think you will be fine just remember to make sure your piggy picks his friend and that they have lost of cage room and neutral ground,grass is great for breaking ice between piggies xxxxxxx