What difference would it make...
...if Severus had a sister, Selina Snape, whom Sirius had romanced and eventually married?
Look Into my eyes - there you'll see - what you mean to me
search your heart - search your soul - and when you find me there
you will search no more
Don't tell me, it's not worth tryin' for
You can't tell me, it's not worth dyin' for
you know it's true, everything I do, I do it for you
What if, the night James and Lily died for Harry, Selina had died in childbirth of a baby girl with her mother's features and father's eyes...?
Look into your heart - you will find - there's nothing there to hide
Take me as I am - take my life - I would give it all
I would sacrifice
Don't tell me, it's not worth fightin' for
I can't help it, there's nothin' I want more
You know it's true, everything I do, I do it for you
What if this girlchild, Sirius having been thrown in Azkaban, was given over to Severus as closest-of-kin?
There's no love, like your love
and no other, could give more love
There's no where, unless you're there
all the time - all the way
What if Severus doubted his capacity to provide for all of the child's (*cough* emotional *cough*) needs? Who could he turn to?
Don't tell me. it's not worth tryin' for
I can't help it, there's nothin' I want more
I would fight for you
I'd lie for you
Walk the wire for you
Yeah I'd die for you
Who might Severus think to trust in a such a critical role... not for his sake, but for the baby girl's?
You know it's true
Everything I do, I do it for you
Black Light and its sequel White Shadows, by Dante Lewis
A deeper look into one of the many interpretations of Severus Snape.