(oh mobile sorry for errors)
Xisuma is the next in line for the throne. Being crown Prince, X had oh so many boring and dry meetings he had to attend regularly. Part of the only reason X can survive these is the time he gets with his advisor and lover, Cub.
Cub didn't seem all that special to the council, he was common born and not very eye-catching (in their incorrect opinion) so they often forget him there. Council members often talk freely amongst themselves when X leaves, forgetting the Vex hidden in the shadows, always listening.
On the outside their relationship souly looks like a cold work partnership. Leaving people to speculate what is Cub really doing and what does he gain from this, as there is no public show of his gain. Others back up these claims with proof of Xisuma seemingly 'too reliant' on Cub's opinion and advice. This leads people to say Cub is trying to be the power behind the throne.
Well all of this simply isn't true. Cub has seen the corruption power can do, and he wants no part of it. On X's part he understands he may be considered a little naive, so that's why he trusts Cub to get him what others won't tell him. As well as the fact Cub has a different perspective that X does. Being a common born, Cub can see things that are between the lies, and is trusted enough to not spin his own. So ofc X will listen to Cub's opinion and advice as it is true and nothing for cubs own gain. In fact if there was anything Cub does want, he wouldn't have to lie to get it, he could just ask the prince himself. And with eyes like those how could X ever say no. So Cub has no need to lie, and as for payment? Well his lover makes sure to treat him right.
Cub always lays out the facts for him - whatever they may be. Financial issues that a noble didn't inform him of, the council's opinion on a latest policy, whispers of a security issue at the wall. Cub hears all of it. He learnt, as a child, how information can get you a lot of things. Whilst he didn't have the best intentions back then, he's left those days behind him.
He just doesn't see the point in lying to Xisuma. He rarely has anything to gain from it, and he'd rather stay in his parents' good graces. Xisuma will be a good ruler when the time comes.
Cub's going to help to make sure of it.