Here is what the conception calculator says, but it will only be as accurate as the method by which you got the due date.
If your due date came from a relatively early ultrasound, this information should be reliable. But if it just came from a count based on the first day of your last period, it won't be quite as reliable.
First Day of Last Menstrual Period: September 20, 2012
Probable Date of Ovulation: October 4, 2012
Possible Dates of Conception: September 30 to October 8, 2012
Due Date: June 27, 2013 (40 weeks)
Sounds like the numbers from the calculator are trustworthy, then. That means the guy from the 4th is by far the most likely candidate. I would still consider getting a DNA test once the baby is born, but it really would be just so you will never have to wonder, not because the guy on the 11th is likely.
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