I can't believe the number of people who are supporting the S2BXH and saying that you're being selfish. WTF?
I understand that your kids need a relationship with their dad, which may mean a relationship with half siblings, but in most cases surely the relationship across half siblings is limited? Only MO as I've never been through this experience, so I'm prepared to be shot down on it.
I personally think this is about your s2bxh gaining some control over the split and scoring points.
I loved what KatyH said about giving him stuff and telling him you're clearing space for lingerie.
Personally, I couldn't be bothered with buying stuff from Oxfam for him. I'd just tell him I'd given the stuff to charity...no offense, but it just struck me as the best thing to do for his current relationship.
I'd then explain that women might not mind cast off men, but generally, with their PFB's, cast off clothes aren't de rigeur.
Then I'd tell him to f**k right off, but that's cos I'm a fishwife
Whatever you decide to do I hope that you manage to resolve things the way you want to. And I'm sure that you'll find much happiness in your future, even if now is a pretty shitty time for you.
Good luck!