What sex are they ? And are any males castrated ?
Gilts are far more likely to settle together than entire boars, but if the males are castrated they might settle because the little ones will automatically give the bigger ones top spot. You'd have to watch for the big one deciding to assert his authority and he'd probably bully the little ones at feeding time

You definately don't want to mix gilts and uncastrated male Kunekunes - they become sexually mature far younger than the bigger breeds and you
would get a surprise litter of piglets.
HTH
Karen