Hi, Dbaby, my felicitations on your illustrious relatives. I said pre-ejaculatory fluid can pick up sperm on the trip through the urethra. It doesn't start with sperm in it, but by the time it gets to the vagina there can be the possibility it contains some.
If you will google Cowper's Gland you will see that the pre-ejaculatory fluid it produces is sterile. But if a guy has recently ejaculated (for whatever reason -- beating off, wet dream, other sex), he will have produced millions of sperm, not all of which is ejected in the initial ejaculation. (Some remains lining the sides of the urethra, a dark, moist, warm environment.) Street legend is that if the guy pees, all is well (the urethra is cleaned out). And that might be true if he has had a chance to pee a few times after having ejaculated. But if not, sperm can live a while in the urethra.
Women have written in on this site "We used the pulling out method and I got pregnant!" Not saying this is what happened to you, but just am saying pre-ejaculatory fluid can contain sperm.
As RockRose said, your chances of pregnancy with a guy who pulls out are lower than with someone who did not, but the timing is troublesome. You could ask the guy if he had possibly ejaculated recently before having had sex with you. Unfortunately, often when asked later, guys either can't remember if they had an ejaculation sometime in the hours before a sexual encounter a while back, (or they don't want to admit it if they did). Perhaps the guy would be able to remember clearly if you asked him.
Those dates are too close to tell, Dbaby. If the first guy pulled out, and you know he did, it makes it less likely he's the dad.
But the problem is, if you ovulated on Oct. 20, guy A would be more likely to be the dad (if he hadn't pulled out) because his sperm would be the first to reach the egg. His sperm were well on the way to the fallopian tube, where the egg would meet the sperm, by the time the egg arrived.
The egg doesn't fertilize the day you have sex, it's several days later. So having sex 2 days before ovulation is the perfect timing - the sperm is waiting there for the egg to be released.
But since he apparently pulled out, and would have only left pre-ejaculate (which does contain sperm) it makes it all confusing.
You'll need a DNA test once the baby is born if it's important to you to determine which of these guys is the father.