"Have you not once for the past six years thought maybe you were wrong?" Darryl tried to talk all her suspicions away. He wanted to make a point with her but she was just too fixated upon the fact that it was his family who did it to her. However, Darryl had gone so far as making Franco and even her own father admit if they were behind the accident from six years ago and yet, he had not found any faults in them. L'Empire also suffered a big blow after the announcement of the last heir's death so he could not find any reason or benefit that comes from killing his child. "I went as far as confronting my father about it and there's just nothing I could find. L'Empire wasn't the one who killed Winter,"
"It was easy for you to say that," Xhemin was becoming more weak and exhausted with the conversation so in order to help herself, she sat on the empty bed before her and started wiping her tears away. "They are your family,"
I know you all hate Xhemin. But let's all imagine we haven't read all these parts yet and get back to the chapters where Xhemin and Ziggy was on the run. If Xhemin sought for Darryl's help and told him about the children, do you think Darryl will not confide to Dannah?
If you'll ask me my answer, my answer is yes. Darryl will surely confide to Dannah and will ask her to help them because Darryl trust her sister.
Now imagine if Darryl did tell Dannah and she was indeed the culprit. Then she could have planned schemes againts Willow and Wolfe at their back.
So in my opinion, Xhemin was right for not telling Darryl about the children. Besides, she herself said in few chapters ago that she didn't intend to keep it from him forever. She was just waiting for the culprit to be found.