How do you ask "Who is your dad" in Chinese?
Both of 谁是你的爸爸 and 你的爸爸是谁 are accepted. Note that when the two words put in the former place written as 谁是, while put them in the latter place written as 是谁. As long as you don't write it as 是谁你的爸爸 or 你的爸爸谁是 there will be no problem for you to use both of 谁是你的爸爸 and 你的爸爸是谁.