Oops im sorry i just saw u already stated ur lmp :)
Yeah i understand about the testing. When was your lmp? And how did u determine you conceiving on june 1st?
I agree on goung to the lab, i am 37 weeks i concieved on june 1st my cycles are every 26 days and my last period was may 17th. Soo i would personally say partner number 2 but like the other girls said, theres no fool proof way of knowing unless you get a lab test.
The best way to find out is going to a lab and having a dna test done
I'm willing to bet most people bet on Partner #2 but honestly, without a week inbetween you have NO chance of knowing at all. The pull out method is no type of birth control regardless of what anyone thinks. You'll need a paternity test. Make sure you avoid the boxed tests as I tried one for my first son, knowing who his father was. I then had to go to a lab to prove I wasn't a liar.
Best wishes to you. :)