Gilbert was born to fight the same type of battles as Roderich, but was a hooligan who did nothing but fight and avoided any marriage. He will do anything to become strong, and believes that he is the best and still "awesome", although he hasn't really succeeded at his goal.
He is very loyal to his leaders, and had a special attachment to Frederich II, known to him as "Old Fritz." He continues to hope that Old Fritz will watch over him and that he'll be proud. It is said though, that he tends to become rather depressed if Fritz is brought up due to this attachment.
Gilbert often refers to his younger brother Germany as "West," and hates Russia. He doesn't get along well with Roderich, and also seems to very much enjoy the company of North Italy. Apparently, he had kept diaries since he was formed, which led to him having an entire library of journals.
Almost all of them start with passages that read "I'm so cool/I was so cool today."