1) Association 2) Fraternisation 1) Fraternisation 2) Fraternism 
Fraternization (from Latin frater, brother) is `turning people into brothers`—conducting social relations with people who are actually unrelated and/or of a different class (especially those with whom one works) as though they were siblings, family members, personal friends or lovers. In many institutional contexts (such as militaries, diploma.....
• (n.) The act of fraternizing or uniting as brothers.
Fra`ter·ni·za'tion noun The act of fraternizing or uniting as brothers. « I hope that no French fraternization . . . could so change the hearts of Englishmen.» Burke. 
[n] - associating with others in a brotherly or friendly way
fraternize, fraternization, fraternizer 1. To spend time with other people socially, especially people with whom you should not be friendly [those considered to be 'enemies']. 2. To enter into a sexual relationship with a person of a different rank against military regulations.
fraternisation noun associating with others in a brotherly or friendly way; especially with an enemy