They'll try anything once ! By 'they' I mean some ex-partners, not all of them, though 'they' seem disproportionately numerous.
Did you have a joint bank account? Even if you can show only that the majority of the money came from you (and your family too, maybe), he still has to prove that he paid the rest or a substantial part of it, to get any claim going and then only to the extent of his contribution. Everything seems against him, even had you been married. The pattern of behaviour suggests plainly, he not contributing in any other way, that that it is very unlkely that he ever made this alleged contribution. It's a very hard burden for him to shift, to make any such proof. It was not in his character to make such contribution. It doesn't sound as though it was wthin his finances; was he at home because he wasn't working or for some other reason (might shifts etc) ?
It does sound that you were to some extent supporting him. even if he did pay something, your support might well have cancelled it out on balance anyway.