I know that this isn't funny for you, but I find humor in it. I'm not trying to be mean it just reminded me of an incident at my parents house. My mom has a Miniature Schnauzer that she had planned on breeding. Noel was going through her heat cycle and my brother had let her and our blue heeler cross (male) at the time out together. He was neutered at 6 months of age and at this particular time he was around 5 yrs. They ended up becoming tied. Don't know how this happened given the size of the dogs, but it did and we noticed (me, my mom, my sister) when we got home. My mom and sister freaked out and I just started laughing. I didn't think it was possible (we used cold water to seperate), but apparently it was.
You have nothing to worry about if he is neutered (just kind of throws you off), but now that you have gotten moved in you should get your girls spayed. If Mikki is in heat that means your other girl is getting ready to go to! Keep an eye on them, and once your other gal is done with her heat set them up an appointment. Just take this with a grain of salt, and one day soon you'll look back on this and laugh, trust me!