[NeuroBeautiful]

Hello Nick and welcome!

I agree that there is no specific age and it depends on the nature of the relationship. However, I do not consider what you describe as sibling rivalry. I may be of a different opinion than others, I'm not sure but this sounds a bit more severe.

Sibling rivalry to me is lighter arguing. The issues may be painful but the actual physical/emotional fighting part is not as prevalent. To me, sibling rivalry might look like a slap and then a slap back but neither questions the love of the other. In my opinion, sibling rivalry is among siblings qith equal power as well. What I mean is physically and emotionally it is an equal "fight"

Im not sure your physical size compared to his but the age difference is pretty big and my concern is that at this age there is still physical fights. This seems more severe than rivalry. I would go as far as saying that's an attack of one party towards the other (him to you) Now, I don't know if you said no to the $50 while sticking out your tongue and saying hahaha no way you loser! or you just said simply and in a neutral tone that you will not lend the money but regardless, it isn't really the equal level of retaliation to then use physical force. That's not sibling rivalry. Sibling rivalry would be to say "oh yeah! Well next time I'm not giving you [insert something he gives you that you want]" It is childish in nature.

I agree that this is something to speak to your parents about if they do not already know. I would say speaking to a school counselor may be helpful as well.