Never been to Yemen but I would never have guessed they be in the top 20 for friendliest countries.
Most people there are quite poor by Western standards, to the extent that they might not be able to afford much food. However if they meet you (a relative stranger) they will insist that they must offer you hospitality and literally offer you the last bit of food they own, meaning they go hungry.
I don't think it gets more friendly than that.