User blog comment:SouthParkClydeFan/Analysis on Lincoln's relationships with his sisters/@comment-28872366-20160921021330/@comment-26901681-20160921023033

Lincoln and Lucy might not share the same interests but they get along really well as seen in Sleuth or Consequences.

Lily has been seen throwing her diaper at Lincoln multiple times. She has been seen spitting at him in Two Boys and a Baby when she didn't want to go with Lincoln. I don't really know if I would call these "interactions" but it is difficult to actually interact with a 1 year old.