The reason it was half-serious and half-playful was that, on one hand, Ye Yunqi was genuinely enjoying the pleasure her brother was giving her with his tongue.
On the other hand, she was also deliberately calling out for everyone to hear, specifically for the two mothers and her eldest and second sisters, because she noticed that they were still holding back, especially her mother, who was supposed to set an example for everyone. So, she had to take matters into her own hands and provoke her mother.
Since the goal was to provoke her mother, it naturally involved mentioning things related to her.
As Ye Fei continued to lick her with increasing intensity, Ye Yunqi's moans became more and more explicit, "Good brother, our brother born from the same mother's pussy, you're so good at this. You're making Siqi feel so good she's about to die of pleasure. Sweet brother, you're our everything, our god of happiness. Mom gave birth to you to bring us joy!"
