Cat came back after 3 days and his brother is a mess

We rescued two fluffy boys from a guy who lied about their age (said they were 8 weeks but when my husband got them home to they were clearly more like 4) and they’ve got some Anxious Attachment Issues. They’re about 7 months old now and the less dominant of the two got out Saturday. His smaller but fiercer brother was a tragic basket case until he strolled back home this morning (Tuesday). Little Brother was ecstatic and they were loving on each other and grooming, etc, for about 15 minutes and then all hell broke loose. If I didn’t know better and they were people I’d say he was FURIOUS with his brother for getting out and scaring us all half to death. They’re both fixed and luckily the dominant one is smaller, so even though big fluffy is not as feisty he can defend himself, but they’ve been fighting like crazy for two hours now. Is this to be expected? Will they settle down on their own, or should I separate them for a bit? I’ve only ever had solo female cats before so this dynamic is new to me.