Ok, what do you all think of this: The baby in the flash forward "Aaron," is not Clarie's "Aaron" but that's what Kate, Jack and the other Oceanic 6 want the world to think. Why? Because the baby is actually the biological child of Kate and Ben. Yes, you heard me correctly. Kate and Ben.
Remember back when Sawyer, Jack and Kate were held captive by the Others? Well, there was that creepy scene when Ben made Kate put on a dress and then have dinner with him on the beach. When she was brought back to the cage where Sawyer was she was all brusied up and didn't want to talk about it. I think Ben raped Kate (perhaps in the same way he raped Rousseau...)
Now there has been all this talk between Sawyer and Kate of "I might be pregnant" - we'll perhaps she is, but it's not Sawyers but Ben's. That would explain why Jack doesn't want to see the baby. Kate names the child "Aaron" so Ben will think it's Clarie's "Aaron" and leave her alone and not kidnap the child like he did Rousseau's child.