Thanks for sharing that, Petra. It does seem odd to me that your husband would be more accepting of "pot luck" - I love that term! - on your first baby, but insistent that he's certain he's the father the second time around. But that's just me.
Yes, I can see advantages, and as you point out, problems, with such a parental situation.
I think your question revolves largely around what you are telling your parents about the relationship as it exists at present. If you've told them about it and they accept it, I'm sure they will eventually come to accept the paternity angle.
Would YOU be concerned as to which one of the two men you love was the father?