Tristan can't let his parents know about Bella and Dax from other people. No one knows more clearly and in detail than himself. If he is the first to tell them, he could tell it in a way he knows they would not overreact.
Moreover, if he's the one to tell them first, he could easily set boundaries to protect Bella and Dax. Even though they know about Dax, he will not allow them to meet him without Bella's explicit permission, and he can guess that Bella will never allow that to happen.
Lewis feels relief when he hears that. Since he knew about Dax, he wanted to tell his son to stop them from trying to arrange a new marriage for Tristan. Still, he remembered Tristan had warned him not to say anything to anyone, including his parents.
Because he was afraid his grandson would be angry, Lewis had no choice but to keep his mouth shut until today.
