Yes you can bond two males together - I have a boar pair myself and there are plenty of others on here who do too.
But, character compatibility is vital to a successful bond and your boar is in his teens which can make bonding harder. If you buy a piggy from a pet shop, then you are risking a failed bonding as you will have no idea if the two are going to like each other. They may end up having to live separately.. If you can get to a rescue centre which offers dating then your boar can choose his own new friend which will result in a good bond and you are much less likely to have bond issues.
Two boars need a cage measuring 180cm x 60cm as they are more territorial and need plenty of space. Do ensure your cage is this size.
Your alternative is to have him neutered, have his six week post op wait to become infertile and then bond him with a sow. Some rescue centres will not bond teenage boars due to the risks so neutering may be your option. A successful bond with a sow still comes down to compatibility so via dating at a rescue is stillbthe safest way to find a sow friend for him, although a boar/sow bond tends to be more stable.
If you are to carry out a bonding yourself, then there is a specific procedure which needs to be followed. The guides below explains further
A Comprehensive Guide to Guinea Pig Boars
A Closer Look At Pairs (Boars - Sows - Mixed)
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
Boars: Teenage, Bullying, Fighting, Fall-outs And What Next?
Dominance Behaviours In Guinea Pigs
Neutered / De-sexed Boars And Neutering Operations: Myths, Facts and Post-op Care