I struggled with the fact that I love Holmescest. Now I embrace it. I ship it harder than Sherlock/John.
Prompt: Anon wanted: "Sherlock invites John to the Holmes' estate for Christmas dinner (under Mummy's orders of course). Sherringford, Sherlock and Mycroft's older sibling takes one look at his two brothers and says 'still sleeping together then, are we?'. John's like 'WHAAAAAT??!' and Mummy's shocked, and the younger brothers start yelling at Sherringford for upsetting Mummy while John chokes quietly on his food."
This is pretty close to that.
http://archiveofourown.org/works/240478