Is my brother insane?

No.  You don't seem too stable though since you obsess over your brother all the time.

Your posting history also shows that you aren't mentally stable.  Worry about yourself and not your brother.

there are multiple explanations for this. primarily, how was your brother's childhood? alot of these thing could be anything from post-traumatic stress to acting out from a lack of attention.

secondly, how old is your brother? and how is he treated by your parents (/rest of your family) now? many of these sound like normal things for a child/adolescent that is just slightly odd (the bleach is a notable outlier here, but that could just be an isolated incident caused by certain circumstances)

finally, insane (at least in this context) is a very general term that has very little scientific/medical meaning. if there is something "wrong" with your brother (meaning he is genuinely mentally ill, either due to his genes or as a result of trauma) it is hard to diagnose unless you are a professional.

if you are concerned about your brothers mental state, i would reccomend a calm and rational conversation to try and let him know that you support whatever he is going through. if he mentions anything specific, you can even try to research his symptoms, though i would be careful with this. as i said, mental illness can only be diagnosed by a professional, and there's a reasonable chance youre brother (or anyone else) would be upset to know you had dont that. however, if he reveals information to you that suggests he is a danger to himself or others, you need to notify someone immediately.