If you're next in line to the throne but your brother currently occupies it, then it's probably going to be a toxic relationship. You're best to cut him out of the picture.
Most people that are "toxic" exhibits habits ingrained from childhood or trauma, they are some time aware of those habits, and the scope of the habits can be relatively limited in some cases or more generalized in others.
I would say that if that person has a "toxic" reaction, they have to be aware that they had a bad reaction, own to it and apologize later WHEN things have calmed down in their heads.
The toxic occurences in the relationship with the person should also be at a ratio where the good feelings/moments with that person are at a bare mininum of 75% vs 25% toxic.
You need time to "recharge" to be able to be patient and understanding with that person when the toxic reaction is aimed at you.
So yeah balance, and if the balance doesn't overall feel good for you, then it's not good for you, cut it.
I have to be more strict with myself cause I'm prone to extremely unhealthy coping mechanisms for dealing with people. I can deal with most bs nowadays and find it amusing at least, but once you get into "I genuinely enjoy drama" territory then you gotta go from my life. So that's kind of a bunch of people off the bat lol.
I was watching The Lion King (original 1994 version) again the other day. Between the violence, death, and Nala's bedroom eyes, I'm not sure how it only got a G rating lol