The third one here looks like a gay couple and their children. I can’t read Russian but somehow I don’t think these posters were advocating finding a nice Chinese boyfriend and settling down in a international communist committed gay relationship.
MATTHEW'S ISLAND
MATTHEW'S ISLAND 
Hi, Matthew. I would like to notify – this is OLD posters. And, at that time nobody been as a GAY. Even in their mind. To be a GAY – this was absolutelly impossible in USSR and China. Moreover, it was criminal offence. And, eventually, absolutelly no popular at all!
So, just natural friendship, and, may be, some good family values…
There have been gay people in every nation throughout history, even Soviet Russia and Communist China, whether or not gay people were prosecuted or intimidated. The word “bromance” in English does not necessarily mean “gay”, it usually just means a strong bond between two men like best friends or brothers.