User blog comment:TheAnimatorCartoonistDude/My First Fan Theory- Lincoln's Adopted/@comment-24535599-20170124011609

By the subtle hints in Ties That Bind, you mean when Rita says they have 10 kids, I think it was Lucy she forgot, cause if you recall in Left in the Dark, Lincoln says she always forgets about her, she says "Story of my life.", implying that people are always forgetting about her.