About 15 years ago we had a German lodger. The original plan was that he would stay with us during the week and return to his family in weekends. I was aware of Franz* wife not being entirely sure about me.
So I expect she was less than thrilled that DH is military and unexpectedly got called up for a 3 month tour a long way away and he would not be able to visit during that time.
So it was me, Franz, and the children.
Franz was absolutely lovely, funny and the boys got in really well with him. One was ten months old.
We went from polite acquaintances to good housemates very quickly. If one got to the shower first in the morning, the other would make them a cup of coffee and leave it in their room. We shared lifts to work
One time I was feeding baby DS in my room, lying down reading. I looked down and there was blood all around his nose/ mouth. I totally freaked out and ran downstairs calling for Franz. He ran up the stairs with his arm towards us (turns out it was just a random nosebleed thank goodness).
I didn't fancy Franz at all, but I liked him very much. One morning he had an interview. He was putting on his tie and was very jittery and kept messing it up. I went over and tied his tie for him. And in that moment there was a bat's squeak of sexuality. It totally took me by suprise as such a thought had never entered my head.
Dh eventually returned (that was awkward as baby DS took one look at him, burst into tears and toddled to Franz).
Franz and his family moved up to where we live and we stay in vague contact.
I suppose what I am saying is that that level of familiarity is perhaps not a good idea for two sets of married couples. At least speaking for myself, I wouldn't do it again. I think I was very lucky that there was no basic attraction between us.
Sorry, I just had to write that out.