I think brother Lee is the father of the baby.
This would explain a lot of things: here are some
why Cindy , on purpose, gave the police a different brush (not Caylees) when they asked for one. She has said she didn't lie -- she just gave them a different brush.
Also, Casey said to her ex-fiance that her brother had come on to her and touched her inappropriately awhile ago....and that she had been sexually abused
Also, after Casey talked to the jail shrink, her mom asked her "did you talk about?" and Casey said "oh, no, of course not.I didn't tell them."
And why Cindy and George wouldn't let her give her up for adoption when she wanted to -- didn't want anyone to find out.
Lee refused, when asked, to give a DNA sample in the beginning
Also, Lee's attorney slipped up once and refered to Caylee as Lee's daughter (instead of neice)
why Casey has said that there are things she can only talk about within her own family
why Casey hasn't ever really bonded with her daughter
why Lee hasn't been given immunity yet -- they might want this to come out as a motive in the trial
Casey conveniently named a deceased guy as her baby's father AFTER he was buried. His parents said they didn't know anything at all about a baby. BUT -- Casey is so into money that if she really thought he had been the dad, she would surely be collecting social security monthly for Caylee. She has not. She didn't even put a father's name on the birth certificate.
and some more I can't think of right now.