After a barrage of ultrasounds, Mary's team of doctors were ultimately unsure of what would come out. And what came out was surprising: conjoined sextuplets! While doctors studied to eventually conclude that they were inseparable. What nobody knew was this group of fused individuals had brains that were directly fused with each other. And they would use their extra thinking ability to get what they want.

Strength
Can communicate with each other directly.

Strength Source
They were born this way.