It grows harder and harder in 2017 to simply say, oh, that's technology, I won't use it.
Without a doubt, the iPhone is the most accessible platform. VoiceOver is built in (just triple tap the home button), every native application is 100% accessible, and a surprising majority of apps which you find in the App Store are also accessible.
This means, though, that your blind relative will have to learn concepts like interacting with the touch screen, which may seem daunting at first, but is extremely doable.

Restricting them to a phone with a traditional keypad may at first seem like a good idea, but will end up limiting them in the long term.

Avoid the Soft Bigotry of Low Expectations.

The iPhone is really awesome. My boyfriend is a total android freak and tries to argue with me on accessibility but iPhone really Win. Also, iPads are awesome with it too since I take pictures of anything I want to see. I make my text bolded, use the zoom feature (in display and brightness) and the triple zoom feature. The iPhone 7+ is perfect for me as the camera enhances better so I can see further. I often times watch TV through my phone camera since my range is 2-6 inches. Another great feature is the brightness. I have serious photosensitivity and the sun totally almost blinds me. (Left eye goes black and right mostly.) so in the sun I can turn it up really bright or turn it down really low at night. Another great thing Is the ability to change text size on most apps. And we can also invert colors and use color filters so it can be mostly black and not white. It's just a great phone over all.