I agree with you that it adds an interesting nuance on him as a person. Like you said, he’s such a decent person and pretty much perfect in many aspects. Perhaps his greatest flaw is pushing himself too muc. Especially with that in mind, indulging in the relationship with Hawk as a person is even more understandable. It’s the one thing he does for himself, his only haven of rest and recuperation.
We the readers have been shown enough of Hawk’s character to be fairly certain he would see through the whole Cynn thing and decide to be with Mari nevertheless, but Mari doesn’t have the same certainty especially in the beginning of the relationship. And he is of course encumbered by a lifetime of always being first and foremost the (current or future) Cynn. So I have no trouble understanding why he would do this.
And yet. Where is the line? What if everything else was the same, except that Liya had died the very beginning? Not by direct order by the Cynn, but as collateral damage in a mission sent by him? Or, what if it had happened because he had given orders that stopping the slavers is always a priority and if some offworlders die in the process, it is a an acceptable loss? Or, that he had sent the Order to get more healers to the palace?
He didn’t, but each of the cases would mean the situation is less forgivable than now (actually now there is nothing to forgive because no bad deed was done. The line has to be somewhere.
I am reminded of the horrible situation in the UK where undercover police officers had been sent to live with activists (“hippies”) to gather intelligence from them, and they lived there for years and formed relationships. At least one of them became a father of a child of one of the activists, all the time under false pretenses. Some of them were convicted of rape, and rightly so, as the relationships would not have happened if the women had known they were informants.
So, is Hawk being in a non-consensual relationship? It’s not the same thing of course because Mari is not hiding his identity for a reason that is against Hawk or means to harm him in any way. Yet if there is any reason to think Hawk might choose to not be the Cynn’s boyfriend if he knew, then it’s glaringly obvious his consent isn’t 100% clear.