Greatsword is the father to swords and grandfather to dagger. He has had a longer life and has amassed more wealth in that time than his sons, and so he has the funds to buy more expensive and nice skins for himself.
Axe and Mace spent their college years playing videogames and only had a C average and so they can’t afford the things Greatsword can, Though occasionally he kicks them down some cash for old times sake. He doesn’t call himself great, he is too humble for that. Just sword is good enough for him, but the rest of us recognize his greatness and the title was made apart of his name.