Bit of background on my relationship with my brother: ever since my teenage years, I could not bear him. I know it is common for siblings to have arguments and misunderstandings, and that's been the case with both of my siblings. However, this particular brother has long since lost my respect and love, due to a number of attitudes, character flaws, mistreatment and other issues that are irrelevant to this question. The point is: I feel no sympathy for this brother and look forward to moving out so I never have to see his face again, but I don't think he's aware of my feelings towards him (note that me moving out might take a few years, whereas he wants this tattoo in a few weeks). While it's understandable he'd still love me and want to be a part of my life, he just assumes I reciprocate - somehow missing my obvious neglect of reciprocity for years. Just to be clear, I've had arguments and misunderstandings - even physical fights - with my other, younger brother, but we still love each other. My problem is this particular brother, and not my family relationships.
A few weeks ago, he caught me by surprise with a request - I'm sorry, a demand - that I design up a tattoo for him. He's made tattoos before, but recently he's converted into a branch of Christianity. I'm no artist, but I know a thing or two about typography, so he came straight to me to tell me, and I quote, that "you are going to make me a tattoo with this religious message and symbol. Please find a nice font and symbol, this tattoo is very important to me. I've always known I wanted this tattoo, and God told me it had to be you". At that point I didn't know whether to laugh it off or hide in concern.
I don't wish to seem religiously intolerant, but I'm not religious myself. While I respect his religion, his God clearly doesn't know me well enough in that I'd never desire to have any association between myself and this brother, especially a permanent one with emotional attachment from his side. He gave me a limited amount of time to find him assets for this tattoo without ever asking if I wanted to do it. Note that he only wants me to find a font/symbol for his tattoo, he's still going to a professional to get it made. (Also note that he knows I would know better than picking Comic Sans - I want to avert conflict, not instigate it.)
While the obvious "just say no" answer might be right at the tip of your fingers, there are a couple complicating factors: he doesn't take "no" for an answer, becoming enraged when he doesn't get it his way (sometimes bordering physical assault, though thankfully I never had to experienced that), and the religious nature of this request makes it basically impossible to say no without either denying his religion or "personally insulting his faith". Yes, he is manipulative and aggressive - I do have my reasons to want distance from him. He's a couple years older than me and much bigger, so I'd much rather not push his buttons. But I am decided not to give him this tattoo design, especially since I'm sure he'll use it to attempt some sort of emotional blackmail or perceived bonding between us in the future.
TL;DR: My brother wants me to make a religious tattoo for him, and his God said I would. I refuse to make it, but saying no to him could make him rather aggressive.
As for the question, though you might have already guessed:
How do I assertively say no to my brother's request of religious nature without starting a fight?
- Not making the design: making it would be infinitely easier for the conflict, but in the long run something I'd eternally regret, so not an option;
- Not getting him angry or in a religious rant: I really don't want to trigger him. This includes questioning the validity of his choice based on whether or not he agrees with Leviticus 19:28;
- Bonus points if he doesn't try to coerce my parents into peer-pressuring me (though that's probably going to happen);
- Extra bonus points if somehow he accepts it in a understanding fashion (the least tension between us the better).
EDIT: As per request via comment: I'm 24, my brother is 26. We live together with our parents in the United States.