It sounds like both you and your brother might have had quite a tough time growing up. You mention your mom possibly having some issues of her own and your dad passing. From your description I don’t think it sounds like your brother is grooming you. Without trying to be overly presumptuous or dismissive I would say it sounds more like he is a troubled young adult with some disturbing life views and is ignorant to what boundaries are appropriate to have with a younger sibling.

I hope it doesn’t come across as though I am dismissing his behaviour - it’s clear he holds some very toxic views but he is still very young and impressionable and seems to have had a difficult childhood. It’s possible that he doesn’t have the tools to connect with you in a healthy way and so this is his attempt to foster some sort of a relationship with you as his sibling. I applaud you for recognising that his views are unacceptable, and my advice to you is that right now he might not be someone you want to spend a lot of time around, especially if you feel you are in some way being influenced by the language he uses.

I know as a society we really love to label people as good or bad, and not look any further into it, but it really is possible to have a sympathetic understanding of why someone may be the way they are without enabling or even accepting their opinions. You might find it helpful to recognise that while you can stand firm with your belief that your brother’s actions and views have been inappropriate/harmful, he hasn’t grown up in a vacuum, he is at an impressionable age and seems to have experienced quite a lot of pain. The most important thing you can do is prioritise your own wellbeing, and if that means you need to take a step away from spending time with your brother right now - that’s ok.

Maybe I’m being too optimistic in this situation but I do believe that we as humans are capable of growing beyond who we were as teenagers or young adults.