actually, for the Ancient Greeks there was no concept of 'homosexuality' because as women were so devalued in Greek life, having sex with a woman was considered something dirty but necessary, whereas having sex with another male was an act of purity and love.
As well, it was typically considered to be the purview of the wealthy and powerful to take young and beautiful male lovers who were, in turn, considered to be blessed to be given attention in such a manner.
This does not mean that men did not have sex with women, or slaves, but the 'ideal' was the romaniticized love between the right men at the right time.
When the Romans conquered Greece, they not only took their Gods, their architecture, mythology, politics and military, they also took their idea of romantisized masculine love ... and nicknamed it 'Greek' love.
There are still cultures today in which men must 'buy' their wives, and until they are able to afford that luxury, take on younger men as 'wives' in the meanwhile. Most of these types of cultures have a very strong 'warrior' life-style which typically romantisizes masuline attributes and physical beauty.