system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: For conjoined twins, how do the two brains control one body?
gpt
Conjoined twins aren't a regular phenomena, so there isn't really a set of rules as to how it'll work out. It's pretty much a case-by-case thing. 

I will point out, though, that it's not really "one body". It's two distinct bodies that are fused together. Each brain controls it's own body, even if those parts are fused to another body.