Red Star Belgrade and Olympiacos might not scream brotherhood for most neutrals across Europe, but their 30-year 'brotherhood' was on full display on Tuesday when both sides met in the Champions League group stages.
It's a relationship which Agona Sport claim started between ultra groups Gate 7 (Olympiacos) and Delije (Red Star) in the mid-1980s.
Although there wasn't any one thing which caused the two clubs to form such a close bond, both Serbia and Greece have a predominantly Christian Orthodox faith, while the clubs also play in similar red-and-white kits.
Before kick-off in their meeting at Red Star's Rajko Mitić Stadium, both sets of fans were locked in chants with each other and there was also a tifo which was unveiled in the stands ahead of the match.
"Let today win the one in better mood, but we will be brothers forever in evil and good," the tifo read.
Olympiacos aren't the only club who have a close relationship with Red Star Belgrade - otherwise known as Crvena zvezda - as Spartak Moscow fan group Fratria have a similar friendship for over a decade.
They might be good friends, but Red Star and Olympiacos will likely be fighting it out between them to stay in European competition this season.
With third place likely the only one up for grabs - Bayern Munich and Tottenham are expected to qualify from Group B - there will be one place available in the Europa League knockout stages at the turn of the year.