I had a nephew like that. He was 2 years older than my daugher and for a couple of years, we shared the same home. It wasn't easy.
If your sister is open, I think it would be wise to discuss how the 2 of you can be consistent on discipline, positive reinforcement, etc. And, both act on it.
There are going to be times where she is in the room and you are not, and vice versa. So, you need permission from her to discipline him just as she would. And, in a calm manner of course. Being aggressive will only feed his aggression.
Unfortunately, I didn't have that communication w/my SIL or BIL and neither did my husband. So, I didn't feel I had permission to discipline my nephew and the 1st time I did, they were upset at me. Then, they wouldn't consistently discipline him. So, there was no consistency and he started to understand when he could get away with things and when he wouldn't. (kids are smart).
Good luck!
S.