A quick googling reveals: "About a third of all people can raise one eyebrow: left or right. [..] But the ability to raise both eyebrows separately is much rare

A quick googling reveals: "About a third of all people can raise one eyebrow: left or right. [..] But the ability to raise both eyebrows separately is much rarer. If you're not among them, that's because you cannot yet control and move the corresponding muscles."