AITA for being pissed off that my brother won't stop whining about what a waste of time our grandfather's will reading was?

I (M 33) have three younger siblings (F 30, F 27, M 25). My sister (F30) and I were born to different mothers, but our dad had kids with the same year so we were raised together as full siblings. Our grandfather, my dad's dad, recently passed away. He was very well off. I won't say exactly how much he left behind, but I think everyone in the family was hoping he'd leave it all to my dad, and then my dad could split it up between us as he saw fit, because he's also very wealthy, and dividing up his family this way must've been a real pain in the ass.<br><br>Anyway, he didn't do that. Instead, he left everything to my brother (M 25). This was a total surprise to me and my sister (F 30), but apparently my brother was the only grandkid my grandfather ever paid attention to. He took him on all these trips, let him move into his house for a month to fix up his classic car, that sort of thing.<br><br>Surprisingly enough, my brother didn't scream with joy and start hiring lawyers to figure out how Wills work. Instead, he called me and my sister up to read the will with him and our dad. I have no idea how he even managed this, but I do know my aunt was left out of the loop completely. We all went up to grandpa's house in the morning, read the will, and went home. The will left everything to my brother. I don't know what exactly it includes, but I'm pretty sure it includes his house, his second job, his social security checks, and probably some stuff I'm not allowed to mention.<br><br>When we were all sitting there, and after we were all sitting there, my brother couldn't stop going on about what a total waste of time reading the will was. Like, he could have known all this stuff on his own, and he shouldn't have bothered getting a lawyer because there's no point in a will if he's going to give everything away, and it's not like he has kids or anything so he doesn't need to figure out who should get this stuff when he's dead, and so on and so forth. <br><br>I gave him shit for it later on, and he and my sister have been at each other's throats ever since, and I'm just fucking sick of it. He won't stop fucking whining about it and my sister can't stop fucking calling him an asshole and a fucking bitch. AITA for being pissed off at him for not stopping with the fucking whining?