Complex sentence: Unknown to Xiuqiang was that when Xiangfei, pregnant with a second child, had left the temple, secretly returned to her homeland, was taken in by the Chai home there, and became a soldier in the Ming Dynasty Imperial Guard, the Jinyiwei.
Split into simpler sentences: Unknown to Xiuqiang, however, was that when Xiangfei had left the temple, she was pregnant with a second child. She secretly returned to her homeland, was taken in by the Chai home there, and became a soldier in the Ming Dynasty Imperial Guard, the Jinyiwei.