Rylan Wilkes

Vail's father (and also The Lighthouse Keeper's father).

-Spoilerish for anyone who believes i will act on this story and make it a comic-

Vail's father stole a Merrow's cap and kept it hidden, because he had been bewitched by her (idk if i wanna call it love probably not). In doing so, he forced the Merrow to live with him and ultimately raise a family with him. She gave birth to twins and he was absolutely delighted. A year after that, he returned the Merrow's cap, hoping that she would still stay. However, she was gone the next morning, along with one of the twins. He was devastated, but took to raising the remaining twin on his own. 

So like, the one that remained was Vail and the one that was taken away is the one that's living in the Lighthouse. The Merrow took a twin because she did learn to like Rylan but still wanted to go back to the sea. It's complicated and she never wanted to be there in the first place sigh. 

Rylan's a nice dude, honestly. A Merrow's allure is just not something a human can handle. In all the time he kept the cap hidden, he treated her lovingly. He knew in his heart she didn't want to be there, but humans dont act on logic anyway, cause we're just emotional stupid fucks. I think he returned the cap because the guilt finally ate him. I dunno.