Does Inter have any special relationship with any other clubs? Benfica are friends with Torino due to the Superga tragedy(we were their very last opponents). Real Madrid also share an historical friendship with us and Santiago Bernebéu in particular was a big friend of ours and would call our club occasionally asking if we needed any help, not to mention Eusébio was friends with Di Stéfano. Eusébio also was godo friends with Bobby Charlton, hence why Man Utd and Real Madrid paid homage Eusébio after he perished. Another club we had some historical affinity with were Hearts from Scotland. Our first ever European Cup opponent, I believe. Barcelona also seem to have respect for us.
And there's also a friendship between the ultra groups of Benfica and Hajduk Split, but that's another story. I don't think both clubs have any sort of relationship on an institutional level.
Our most famous relationship is with Lazio, although it is deemed "useless" by many supporters of both clubs - especially since Roma and Milan no longer get on with one another and particularly since Lazio have appeared to favour Juventus in recent years. We used to be twinned with Fiorentina at one stage, but that fell through when we bought Nicola Berti in the late 80's and we even became bitter rivals when their president fell out publicly with Massimo Moratti some years ago.
Apart form that, we are officially twinned with Nice in France since 2015, because one of our "ultras" signed for them as a striker!
We are also friends with Valencia even though a Champions League match between the 2 teams ended in a brawl 10 years ago. There is also a bond between Inter and local team Varese, mainly to counter the relationship between respective derby rivals Como and Milan.
The relationship we are proudest of the most however is with The Kop at Liverpool. I'm not sure exactly why or how this came about. I think it may have something to do with Benitez and/or the fact that we housed many of their fans in the CL match against Tottenham in 2010, although I am unsure why Liverpool supporters would want to go and watch a game between Inter and Spurs...