User blog comment:AustinDR/The Worst Theory?/@comment-24200891-20171015054334

I don't believe Lincoln is adopted. If he were, then why the sisters don't talk to him about it? Because parents forbid them or the parents did everything in such secret the sisters would never know.

Some believe in theory that Lori is Lily's true mom and the parents pretend Lily is their daughter to avoid scandal. It's not impossible, but it's unlikely.