Shounen-ai is an obsolete term. Shounen-ai refers to stories about strong
relationships between pubescent or pre-pubescent boys. The stories featured angsty, poetic, platonic or romantic
relationships. It is used only to point to shoujo manga written in the 70's and early 80's by authors such as Hagio Moto, Takemiya Keiko, etc. (Titles such as Gymnasium in November, Heart of Thomas, and Song of Wind and Trees.) Shounen-ai is no longer written, ceased to exist as a sub-category of shoujo long ago, and this term has long since fallen into disuse. Later stories with male/male sexual
relationships are termed yaoi, tanbi, june, or boys' love.
Shounen-ai is NOT the same term as boys' love.
The current common usage of shounen-ai in Japan is to refer to adults who like young boys (i.e. pedophiles).