#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

my %relative;
while (<>) {
    my ($close_relative, $of_interest) = /(.*)\((.*)\)/ or next;

    next if $close_relative eq $of_interest;

    undef $relative{$of_interest}{$close_relative};
}

for my $gene (sort keys %relative) {
    say join ' : ', (keys %{ $relative{$gene} })[0], $gene;
}