Many sows will accept younger pigs but not always, I have stock fencing between my pens which helps to know who likes who! If you were to introduce a couple of little weaners I would guess they would be ok, particlularly if you are keeping a weaner to breed from she would still be young herself, of course expect a pecking order to establish, but they do like company and would soon settle.
Sorry forgot to hello and welcome! how rude of me!