The formatting strongly resembles the naming conventions used on unauthorized file-sharing or piracy websites, where numbers like "787" or "108" often refer to encoding releases (e.g., "1080p") or arbitrary file identifiers. Additionally, "SSIS" is a known production code prefix for a Japanese adult video (AV) studio (S1 No. 1 Style). Combining "SSIS" with familial relationship terms ("father-in-law") strongly suggests content that is produced, scripted, and performed by adult actors, often within specific exploitative or taboo genres.
It is important to clarify that the string of text you provided ( ssis787 eng sub my abhorrent fatherinlaw108 better ) does not correspond to a known, legitimate film, television series, or published literary work as of my latest knowledge update. ssis787 eng sub my abhorrent fatherinlaw108 better