Ok, so in Light and Shadow, MC's husband had a younger brother, who MC saved as a child. That brother became king of Ulswald. He married a young noble (from Northrian) even though she was barren, saying that's perfect, since the king intends to pass the crown to his nephew (Alex, current ML in Golden Time) anyways, and would prefer to avoid any inheritance conflict which would ensue if he had offspring of his own. That noble the king married is Katrina. She didn't have a big role in L&S, so we only see her for about 3 chapters, if I recall.
I’m pretty sure she was the one that got married to Eli’s brother, I always forget his name. But all I can remember is that she can at the end of Light and Shadow
Oo ok ty
refresh my mind who is katrina again and was she in light and shadow