What I discussed in my previous post has been assumed by most scholars to apply only to relationships with a male patron and a female concubina. The masculine form of the term, concubinus, is frequently explained as the term for a young male slave used for sexual release until his master married. Usually no other possibilities are given. This is very often exactly what the term refers to. In Catullus 61, for example, the bridegroom must set aside his concubinus for his bride and to not do so would be to cling to childhood.
This is not the only possible situation described by this term and there are several things worth questioning about such a narrow definition. The fact that the same word with a different gender was used in both cases is also a definite point in favour of this argument, though not a strong one. There are examples of Latin words that could be made to mean different things simply by changing the ending. That said, the problem Roman society had with the idea of a man marrying a man was the idea that one many would have to lower himself to act the wife. In a relationship of concubinage, the lower status partner would not necessarily be considered to be lowering himself further.
Regarding the interpretation of Catullus 61 I’d like to point out that a man was not required to be sexually monogamous. He could have all the sex he wanted with his slaves, regardless of his status. Additionally, it was also common for a young man to have a female concubine whom he would dismiss upon his marriage. Catullus makes no mention of the slave status of the concubinus. What makes these two relationships any different?
There are many similarities between the usage of concubina and concubinus. To assume the narrower definition of concubinus is the only accurate one and to assume that it could only be a sexual relationship with no comparison to marriage (as is implicit in the female form of the term) is to force history to conform to our modern views and to ignore the way Roman society worked.
Concubinage - Wikipedia
Catullus 61 - Perseus Digital Library (Note: This particular translation uses the word “favourite” for concubinus. This is not how a Roman audience would have understood it.)
John Boswell's Same-Sex Unions in Premodern Europe also provides some discussion of this term in its chapter on Ancient Rome. Just bear in mind that this is not the primary topic of the book.