How to present an optional binary choice without a preset value?

How would you go about approaching a form where the user should pick one of the binary choices (yes/no) in the UI, but it should also not be enforced to block advancement within the flow.

So basically, an optional binary choice. Either YES or NO, or nothing at all. Using a standard checkbox wouldn't probably be efficient as the value would by default be seen as false if unchecked, and not "require" any action from the user if they intended to reply NO.

Our current approach (in the Android world) would be radio buttons (presented horizontally), but it still feels wrong. My iOS counter part is using something like a segment toggle, as radio buttons don't really exist on that platform.

How would you go about doing this (but not this?) in a good fashion?

Follow-up question: what about iOS? Is the segment toggle the way to go?

Edit: We would prefer that the user just picked between YES/NO, but if they skip picking altogether that's OK for now.