In an interview with Christian Antidormi, who portrayed Tiberius, he declined it and said they are just best mates.
John: I guess some fans were wondering if there was a love relationship with your childhood friend, Sabinus. Are they just friends or are they more than that?
Christian Antidormi: That’s a question that hasn’t really been presented to me yet, but I know that in minds of a lot of people that is the case, and in the end that is the purpose of the production. We wanted to instill a lot of confusion around the relationship between Tiberius and Sabinus early on. There were a couple of moments there that were meant to keep the audience guessing. At the end of the day Sabinus and Tiberius were just best mates who were willing to slug it together in war and there wasn’t really anything else going on in that sense. So sorry to disappoint to a couple of fans, but it was definitely supposed to spark some sort of interest in regards to the potential of their relationship and ultimately during the war it was destroyed.
He also declined it in another interview,
Metal Arcade: Do you think that Sabinus maybe liked Tiberius as more than just a friend? A lot of people have speculated about this.
Christian Antidormi: To put it simply, no. It was a strong brotherly relationship, they were willing to do anything for each other. Props to the writers for purposefully inserting little moments of curiosity. It sparked some interest and speculation in regards to, ‘Ooh, are they? Aren’t they?’ It was sort of interesting, and the way it was written, I guess we were destined to never truly find out. But at the end of the day, they were brothers who were willing to die for each other, and you know that was it.
While that dialog may hint romantic feelings towards Sabinus, there is nothing as such. It's the writers who succeeded waking up some curiosity and sparking some speculation.