All piggies need to be compatible to have a functioning bond - sows can fall out just as easily as boars do, but boars can be a little trickier. Your previous pair were obviously very well matched.
Teen boars can just be harder work once hormones kick in so: ensuring they have a lot of space (a 6ft hutch is great for them), that all hides have two exits so that no piggy can get trapped inside an area and that you respect their hierarchy and always handle the dominant first. However, compatibility comes first and if they dont get on then nothing you do is going to make any difference to that unfortunately.
Let us know how things go at the vet