Any thoughts on the somehow cannon Blossomthorn? Seems like an interesting dynamic, both were in the DF so I imagine there is some camaraderie of that
I imagine that Thornclaw really wanted to sire some kits before retiring because it was the last thing on his checklist of things that warriors do that he hadn't done yet. I picture him being kind of awkwardly formal in his "courting" of her because he's an old-fashioned Old Forest cat.
On Blossomfall's side I think it was more of an opportunistic thing. Like she was feeling like it was a good time for her to have a litter, and an eligible senior warrior bachelor came sniffing around. In an objective sense, Thornclaw probably rates as a quality mate: well-respected, hard worker, senior warrior.
Perhaps their shared experience in the Dark Forest let them bond a bit, and I imagine they like to gossip together because they both seem like the type to. They also both have a fierce side, which I think could let them challenge each other (and makes the act of mating vigorous and passionate). But by and large I think of it as more of a pragmatic pairing of circumstance rather than a true romantic relationship.