Shacklebolt was a Sacred Twenty-Eight family. Did that mean that Kingsley had been approached too? She couldn't imagine that Rodolphus would just ignore the fact that there was still at least one Shacklebolt alive. He was the sort to want to possess an entire set. If he found Kingsley and tried to persuade him to join, it would make sense that Kingsley would encourage her to find out what Rodolphus" plan was before deciding it wasn't worth pursuing. She needed to share what she knew with Antonin. He would know what to do next.