Two great mathematicians of the 20th century, Pavel Alexandrov and Andrey Kolmogorov, were the closest of friends. They were almost certainly more than that too, although we cannot be sure. Understandably, they guarded their privacy closely due to the terrible persecution of homosexuals in Russia at the time.
Alexandrov said [pdf] of their relationship:
“in 1979 this friendship celebrated its fiftieth anniversary and over the whole of this half century there was not only never any breach in it, there was also never any quarrel, in all this time there was never any misunderstanding between us on any question, no matter how important for our lives and our philosophy; even when our opinions on one of these questions differed, we showed complete understanding and sympathy for the views of each other.”
No quarrels, no misunderstandings, complete understanding and symapthy for 50 years…. that really sets the bar for the rest of us.
Simple City 
dear richard, i found you on plus but they refused to post my comment about one of your articles. so i’m writing you here .. i cannot recall all the truly nice things i said on my post there. but i’m sure you can retrieve them from plus if you ask nicely 😉 anyways, i make a friendly challenge you and i have a similar friendship you quote above 😉 what’s there to gain? only we can find out 😉 another website of mine is: http://www.nowpublic.com/sam-micheal i’m sure you’ll find the stuff in the very least entertaining to read 😉 yours truly, sam 🙂