If he is 7 years old and is being toxic already, maybe they should not be allowed to be on video games.
Also, their friends are probably a bad influence. Also seeing as if it actually was your brother and it isnt just you trying for a pity party in the place that absolutely has 0 chance of helping you out aside from telling you to try Riot Support..... then you had a 14 day already for some reason.
I am assuming it was toxicity. Along the same lines as what probably was shown in that last game.
So either it was you, or your brother was doing it because you were doing it. Be a better role model for your brother.
But I do not believe someone should get out of losing their account just because of an excuse that is the equivalant of "my dog ate my homework." When obviously what was said was very deserving of the punishment seeing as you are willing to say it was toxic but not even post chat logs.