My (30F) brother (35M) needs an organ transplant and it's ruining my life, but not in the way that you think.

Before I get started with this post, let me mention that I had originally made this throwaway to post about my dad being a jerk about my wedding a few weeks back, but decided against making a thread.
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My older brother has always been unhealthy to the point where he probably adjusted to a baseline of feeling crappy, so he didn't end up getting diagnosed with kidney failure until recently when he was hospitalized after losing vision in one of his eyes after a car accident. When he was there, they learned he has abnormally high blood pressure and also as mentioned, kidney failure.
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I am his only sibling and only family member eligible to donate, if I am a match. Our parents are too old. I work for my father and would be able to take the time off work for surgery easily, as Dad (70M, if it matters) would just do management stuff in my absence. I love my brother and would do absolutely anything to try and save his life.
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My mom (early 60s F) has got the idea in her head that instead of my being tested and offering my organ for transplant, I should drop out and have them test other people instead, so when he needs another kidney in 20-30 years, he can have mine then. The highest probability of a match is me, his sibling. As well, if I drop out now, we don't even know if I am a match. They only test one person at a time, where we are located. S
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My mother's perspective is this: She doesn't feel capable of being a support system to both of us whiles we recover from surgery and would be upset if we both died.
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I have some objections to that: Regarding the "support system" argument - I have a fiance and my own home. If I need a caregiver in my mom's stead, I can reach out to my mother in law, who is retired. If we wait 20-30 years, my mom and my MiL will probably both be dead so maybe I would have even less of a support system. I don't know where I will be or how my business will be being run. I also don't know what health problems might crop up between now and then. Right now I am healthy. I have the ability to take an extended period of time off work. I also feel uncomfortable with the idea that in an undetermined amount of time, I would be called upon to donate my kidney on command, rather than making the choice myself now (again, IF I match). My brother might also have a child or children by that point, who would also have a decent chance of being a match.
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Thinking about having the opportunity to save my brother's life, NOW, and declining to do it, or having him decline me as a donor (which he is allowed to do) if our mom bullies him into it (which she is capable of doing, he's a mama's boy) makes me so angry I can barely breathe.
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Can someone help me understand her perspective? Am I the one in the wrong here? I'm so angry and so scared that my brother's life is being put at risk because my mom is being so selfish.
TL;DR: Brother needs organ transplant, mom might try and stand in the way of my donating. Help!


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