Making random kid-oc's for every Snape-ship cus I can.
Sirius × Trans Man!Severus.
Having the kid during the first war because of a one night stand, Sirius had no idea about them, the reason for Severus not dirtying his hands being single parenting the kid.
Severus names the kid Astarion (which is basically little star/son of star) (Sirius taunts Severus over it upon finding out after Azkaban ("oooo you're not over me"))
Narcissa finds out that Sev has a kid when Lucius mentions it casually.
She's so not casual cus that means a playdate for Draco.
She notices the Black Family features, poor Sev can not keep that secret from her, but all she wants in return is the playdate for Draco.
Sirius doesn't belive it's his kid at first during OofP until they out-sass him. But the kid also hates him since they were raised by Severus.
Do with this brain blabber as you wish.