9 Huit is the (presumably) last Huit child to be born. Her eight siblings are octuplets, but she was born eight years after the rest. 

Development and Accelerated Power

During Lucy Huit's ninth pregnancy, she was teleported into the miniature world of a snowglobe, which may have affected the developing child, for shortly after birth, 9 displays her telekinetic abilities, while these took a minimum of eight years to reveal themselves in her siblings. This could also be due to the breaking of the inherent Symmetry of the family's reality, which is broken by 9.