The most crucial factor was his own lack of confidence back then. Niamh had gone so far as to fake her own death just to escape him. Why would she ever have kept his child? That’s why, in the beginning, Jonathan hadn’t let his mind go there. He didn’t dare. He couldn’t bring himself to believe that Marlin could be his and Niamh’s son.
But as time went on, especially after he and Niamh arrived in Coralis, he felt more and more that something was off. Although Flynn had been playing the part of Marlin’s biological father, his performance was terrible. He not only showed no interest in pursuing Niamh, but he also lacked the natural, blood-bound affection a father would have for his son. It was easy to tell the difference between genuine feeling and pretense.
In Jonathan’s eyes, even if Flynn had once had designs on Niamh, he was now nothing more than her employee—a simple boss-and-employee relationship, and nothing more. As for Marlin, to Flynn, he was just the boss’s kid. That was all. Jonathan could tell when a man was interested in a woman, and he could certainly tell if a child was his own flesh and blood. He knew Niamh had lied to him.
And the only reason she would go to such lengths to have Flynn pose as Marlin’s father in front of him was that Marlin was, in fact, his son. Jonathan had only recently pieced together the truth, but from the look of it, Elmer had known for some time. If he remembered correctly, Elmer had only just arrived in Coralis with Lana and had only recently seen Niamh again. That must have been the first time Elmer had met Marlin. To deduce that he was the biological father after just one meeting… Jonathan had to admit, Elmer was sharp.
“I never realized you were so perceptive.” Jonathan’s words were meant as a compliment, but Elmer’s face showed no sign of pleasure. Instead, his expression soured slightly. “Because I know Nia better than you do,” Elmer retorted, his tone sharp.
Jonathan watched him, not quite understanding what had upset him. “Yes, I admit it. You know her better than I do.” It felt like the first time Jonathan had ever conceded anything to Elmer, but the displeasure in Elmer’s eyes didn’t fade. He was seething inside. His claim of “knowing Niamh better” was really just a way of puffing himself up. It was the only area where he might have an edge over Jonathan. In terms of the depth of his feelings for Niamh, he fell short. In terms of his importance in Niamh’s heart, he couldn't compete either.
Elmer shoved a large spoonful of ice cream into his mouth, the cold sending a shiver through his entire body. Jonathan tried not to laugh at him but couldn’t help but let a small smile escape. “I finally understand why Niamh was able to stay friends with you for so long.” “Why?” Elmer mumbled, pressing a napkin to his mouth, wishing he could spit the ice cream out. “Because even though we’re rivals, you were willing to tell me that Marlin is my son… Thank you, Elmer.”
Elmer moved the napkin away and looked at Jonathan seriously. “You don’t have to thank me. I didn’t do it for you.” He did it for Niamh. He wanted her to be happy. And he knew now that he wasn’t the one who could give her that happiness. It was a bitter pill to swallow, but he knew that person was Jonathan. “So, what’s your plan? Nia still thinks you don’t know Marlin is your son. Are you just going to pretend forever and never acknowledge him?”

Comments
The readers' comments on the novel: His Housewife Had Secret Identities