I do not see a reason why frindship can not be between males and females but we need to be clear about a number of things
Maturity of both is a must to keep the relation within the frame of friendship
Clear expectations from both parties, need to be set and boundaries agreed
If the relation was to develop into something else, are they ready for it ...
Culture differences ...
All these factors define the nature of the relationship
In my country they say do not place fire beside petrol and do not expect it to burn ... I have learned that setting the rules can make it happen
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