The reason Fu Xiyan suspects that Gu Zhiqi is his real sister is because, last year, he saw a paternity test at Jin Huazhu's place.
The test was between Jin Huazhu and Fu Yingying, and the result was: Fu Yingying and Jin Huazhu are not mother and daughter.
When he saw the result, Fu Xiyan found it somewhat unbelievable.
When his mother was pregnant with the third child, Fu Xiyan was already seven years old.
He clearly remembered the image of Jin Huazhu with a pregnant belly.
The child was born by Jin Huazhu, how could it possibly not be Jin Huazhu's biological child?
At that time, since Gu Xiyue had just returned to the Gu Family not long ago and witnessed a real-life case of swapped children, instinctively, Fu Xiyan also began to suspect whether his family's third child was swapped with someone else's.
Thus, he secretly did a test between Fu Yingying and his father.
But the test results showed that they are indeed father and daughter.
