My family can also be big "triggers" but..well, dealing with the discomfort of feelings is what sobriety is all about. Given you lost your mom and well, your brother is discharging his own pain by "blaming" you (unrealistically at that)..well, ya ..everybody's emotional here and it's a loaded subject.
You have to come to the decision you are going to deal with the emotions by whatever means possible if you are going to sober. Triggers happen...all the time. We put together sobriety by dealing with them...one at a time.
You can do this if you decide you are going to face each arriving situation...sober.