(Minor corrections, March 2013)

Disclaimer: I am not J. K. Rowling. I do not own Harry Potter. If I derive anything positive from this other than occasional satisfaction from reading a nice review or from looking at the Traffic Stats, I know nothing about it.

Note: Just a short piece where Harry is Harry Black, the son of Sirius and Lily - a random thought which occurred to me when I should have been writing something else, to which I will now (hopefully) return. This piece is a one-off. It is somewhat alternate universe.

"Remind me again why you want to invite your aunt and your grandmother to this birthday party?" Harry's father scrunched up his face.

"Because they're exactly like one another, but the one's a muggle and the other's a witch." Harry said. "And I want to see which of them explodes first if we put them in the same room as each other. And besides:" Harry adopted a faintly defiant and stubborn expression. "I've sent the invitations out now, and they both replied. You can't stop it."

Harry's father wondered (yet again) if, perhaps, his wife had had a point when she'd suggested that they simply elope to France and live in passionate sin and skip having children? Unfortunately, living in sin on his uncle's money hadn't had very much appeal to Harry's father at that time – he'd wanted to lay the whole world at the feet of the lady who had since then been his wife for the past dozen years, or at least as much of the world as he'd be able to get his hands on.

And the only way in which he'd been able to do that was by means of legitimate children. His family were prepared to overlook a union with a muggle-born and to figuratively hold their noses if they were in the same room as her, in the interests of securing the dynasty for the next generation or two.

And Lily had insisted that part of any having-children-deal was Sirius taking at least his fair share of work when it came to parental things. Her notion of 'fair shares' apparently involved his doing at least three-quarters of the work after the age of three had been passed, because she did so much of the 'groundwork' for 'securing the dynasty'.

At least Kreacher was resigned to 'muggle-born mistress' these days, and didn't even think about referring to her as a 'mudblood' any more. Kreacher had had a change of heart round about the time that the twins were born, and they needed to reorganise the house so that the nursery was in a bigger room. And Kreacher was apparently genuinely enthusiastic about all the Black children, even if they were half-bloods. What was important to Kreacher was that in terms of children he could see that House Black was growing strong again, and that he had insane quantities of work to do.

Sirius suspected he'd even caught Kreacher with something resembling a tear of joy in an unguarded moment round about the time that Rowena had been born, although Kreacher of course claimed it had been a speck of dirt, because he'd been cleaning so hard.

But still, putting Walburga Black and Petunia Dursley in the same room as one another was just asking for trouble. It reminded Sirius of some of the mischief of his youth when 'The Black Knights' of Slytherin had tangled with James Potter's 'Marauders' in prank-wars in the halls of Hogwarts. Later it had turned serious of course – James just hadn't been able to stop himself from always upping the ante in the face of 'slimy Slytherins' and Sirius and his younger brother and their 'footman' had had the honour of the Blacks to defend, which meant that they weren't going to back down.

"Very well then, Harry, since it's your party, and I said you could invite whomever you want, I shall allow this to stand." said Sirius. "But this is your party, and consequently I expect you to be responsible for ensuring that your other guests do not suffer because you have put your Aunt Petunia and your Grandmother Black on the list."

Harry grinned at getting his own way and then started to look worried, as the immensity of the task which lay before him began to hit home.

Sirius figured his eldest son would work something out. Sure, there'd be a 'diplomatic incident' of some sort, and Sirius' wife likely wouldn't speak to him except in the frostiest of tones for about a week, but Harry would find some way to minimise the damage. He'd inherited practically all the Black charm, but thankfully at least some of the sense of his muggle-born mother, too…

Author Notes:

This was just a random idea, and I don't have very much of a grasp of the universe which it occupies. The likeliest way that it seems to me that this came about was Sirius was sorted into Slytherin instead of Gryffindor and felt sorry for Severus and ended up taking him under his wing (which is how Sirius came to know Lily, who still placed in Gryffindor). Lily remained a best friend with Severus, but never got romantically involved - Sirius was much more interesting a prospect. Sirius may have been sorted into Slytherin but didn't care too much for Voldemort and company and kept himself and Severus out of that stuff. 'The Black Knights' (Sirius/Regulus/Severus) were Sirius' response (probably formed in September 1972, once Regulus arrived at Hogwarts) to James Potter's Gryffindor 'Marauders' (likely Remus/James/Peter).

I'm not sure how Sirius persuaded his mother to put up with him marrying a muggle-born, but clearly he did manage it somehow. Some sort of 'it's for the good of the family' line of persuasion was likely involved.

Neville Longbottom is The-Boy-Who-Lived in this universe. The Blacks didn't fight Voldemort – well not overtly. Sirius may have instructed his retainer, Severus, to infiltrate and sabotage the Death Eaters from within for him, following an unfortunate incident involving Regulus...