Board Thread:Questions and Answers/@comment-26572409-20150704135123/@comment-8986886-20150709160552

@Zeretzu

You have a point but, on the other hand, Ichigo never showed any signs of having Hollow powers until after Rukia's power transfer and Shattered Shaft, which acted as a trigger to awaken his latent powers. It could mean that it takes a similar "trigger" event to awaken the fullbring, and that the younger siblings of Riruka and Jackie simply hadn't experienced such an event yet.