How can I tame my hamster in such situation?, Hamster Lovers (Training)

Hello there all the hamster lovers.

I have some problem in taming one of my pair hamsters. Can someone give me some suggestions?

Here's the situation.

Initially, I bought a pair of male WW hamsters around 1month+ ago. However, they fight with each other. I did try to exchange for another hamster from the shop. I named them "big brother" and "little brother". Unfortunately, they still fight with each other. When I try to stop them from fighting everytime ( which happen like 2-3weeks ago ), the "big brother" hamster bite me. I have already separate them into two different cages awhile ago ( 2weeks+ back ). However, the "big brother" seems to be still quite unfriendly to me. Sometimes I try to clean his cage for him, he will try to bite my hand or make some little noise. The other "little brother" is perfectly fine... I can tame him eat on my hand. So I'm wondering any pro here can teach me some way to tame "big brother"?

Thanks for all the guides.

Cheers.