Yes, with a multiple entry visit visa, that is not a problem. For a PR visa however, one must include all their immediate family members, that's spouse and children. If any person is excluded from the PR application, that is seen as misrepresentation and very serious business to immigration. If people get married or have a new baby after getting a visa issued but before landing and they still go and land on this visa, they will never be able to sponsor the relative in question and may even lose their own PR if immigration finds out what they did.