What they do know about their powers is that they are caused by a relatively rare, anomalous gene. Someone with this gene can be either a Level 1, 2, or 3 anomaly. Level 3 anomalies can go through their entire lives and never be affected by the gene.
Level 2 anomalies can subconsciously use their powers throughout their lives. They have no control over this power at all. However, it is possible for a Level 2 to become a Level 1.
Level 1 anomalies know they have their powers and so can control them.
Since the triggering of their own powers, they have also triggered the powers of their siblings, Taylor's girlfriend Rachel, and two brothers from Boston named James and Blake.
They have strong reasons to believe that Isaac has a fifth power. One that, (at least, when enhanced by James) slows his aging process, stops him from feeling pain and aids in healing.