Character Analysis
In Old English, the name "Hygmod" might mean something like "mindful spirit"—not a bad description of this character. Wealtheow's brother is ambitious enough as king to want to kick Hrothgar's butt, but he's smart enough to know when he's been beaten like a dog.
(The jury's out on that pet bear, but at least Hygmod knows how to make an entrance.)
We don't know much about Hygmod, except that he's willing to give up his beloved sis to save their people from ultimate destruction. But don't be fooled: one day in the not-so-distant future, Hygmod will have the manpower and the cash to take Hrothgar out. Both of them know that.
Hence Hrothgar's no-holds-barred style of negotiating on the battlefield: he can't afford to have an adversary as strong as Hygmod biding his time until that day comes (98). Now that Hygmod has left the best thing he has—Wealtheow—in Hrothgar's keeping, Hrothgar can keep Hygmod on a leash. Or so he thinks.
A Ticking Time Bomb
It's totally possible that disaster could happen at any point in Hrothgar and Hygmod's relationship—notice that when Hygmod glances at Hrothgar, his face is "like a knife" (107). If disaster does happen, Wealtheow will likely be the big loser. In any attack, she could lose husband, sons, and brother, all at one time—but that hasn't happened yet.
When we see brother and sister together in the meadhall, it's kind of a Hallmark moment. They are young, beautiful, and happy—the closest thing to a functioning family unit we see in the whole novel. But the fact is, they really can't be together—and they have Hrothgar to thank for that. It's pretty clear that one day, Hygmod will figure out a way to get Wealtheow back.
Hygmod's Timeline