1) Mycroft isn't strictly Christian, but he is Agnostic and has been since he was fifteen; the last time he prayed was at his little brother's side when he ODed again, just as Mummy Holmes had instilled in him with all those Church goings.
2) Mycroft lived in fear of only seven men in England; two are dead, and two are Sherlock and James Moriarty. And the remaining used to be his closest friends.
3) Mycroft's father was a terrible drunk, and Mycroft, when something that even he cannot take happens, falls into the same trap. And he hates himself for it.
4) Is NOT a virgin thank you very much. Indeed, Mycroft has set his own system of coping with such things rather than his little brother's way
.God knows why he is like he is, Mycroft has never asked and honestly would rather not know.
5) Loves Mummy very much, though she is also completely insufferable.
6) When he was a young man, he was much like Sherlock and had plenty of his own rebellious fun; however, it wasn't as self-destructive and attention-seeking. Also, Mycroft and his friends knew how to keep things secret.
7) Mycroft took a long time to stop swearing. Now, it's a like a switch. When he was a boy in classes he was a veritable angel (or close to) and out he was...well, I would have to swear to describe him.
8) Mycroft was involved in many missions and covert ops. To his mind, he has killed hundreds of thousands on men. In truth, he has killed around 21 personally, though it is hard to tell.
9) Has scars (not including flu jabs) one between his shoulder blades (a burn mark), one on his right hip, and one on the bottom of his left foot, some faint tiny discolorations on his hands, but then the ones few see are the ones on his back....you'd have to inspect him with a light and stare at him from a few inches away but they are there.
10) Mycroft watches you; yes, YOU occasionally. Just to make sure you don't cause trouble.