You can try a bonding bath - bathing both boys with the same shampoo to wash away all the testosterone stink and make them smell the same.
However, I would like to point out that any tricks of the trade work only for a very short time (a few hours max). After that, it is down to wether they are character compatible or not. You simply cannot mask their personalities and true feelings forever and force a liking where there is none, however much you try! Anybody who has been through a number of bondings has had to learn that bitter lesson.