It's difficult to speak of the Slavs in 'Antiquity'. First, we need to be careful not to understand ancient identities as we understand modern ones. One of the dogmas of modern nationalism is that nations are in some way equivalent to languages. This discourse can be seen clearly anywhere from France to China, from Eastern Europe to Australia. Language is seen as a way of defining, legitimizing, and deciding who constitutes a nation, so that the Russian Empire and the Soviet Union suppressed the Ukrainian and Belarusian languages in order to bolster the "Great Russian" nation, and France suppressed minority languages like Occitan to create a unified French nation, and the American and Australian governments undertook policies designed to eradicate native languages to ensure the integration of their would-be speakers.

My point is, language is very closely bound up in national identity for us today, and so we need to be careful not to read these attitudes into older periods. As part of that effort, we need to clarify what we mean by "Slavs", exactly, and for our purposes here let's simply use the term to mean "people speaking some Slavic speech variety". You ask whether Poles and Rusians "recognized that they belonged to a greater Slavic whole", and I just really want to make clear that we have to be absolutely certain we're not assuming the answer in asking our question. What is this "greater Slavic whole", anyways? The inheritance of their language? We might as well ask if Balts and Slavs in antiquity understood themselves as being part of a "greater Balto-Slavic whole", or if Celtic and Italic speakers understood themselves as being parts of a "greater Italo-Celtic whole"--we can go further than that, but I think the point is made: any speaker of an Indo-European language shares a kind of relation with any other speaker of an Indo-European language, and there's no reason to presume a kind of affinity on that basis.

It's hard to talk about Slavic identity in antiquity. First, linguistically at least, the Slavs started to divide into separate groups (East, West, and South) around perhaps the seventh or eighth centuries. Second, we only have endogenous sources from the 9th century, and before that we have a variety of mentions from primarily Greek and Latin writers, and nothing terribly useful for our purposes here.

So how did medieval Slavs relate to each other? Serhii Plokhy has a nice analysis of the identity of the writer(s) of the Primary Chronicle where he discusses the way the Chronicle describes various tribes. There are a whole lot of names that Nestor (the traditional author) mentions: the Slavs, the Rus', the Varangians, and the Polianie, to name a few. Plokhy quotes Nestor,

While some Slavs were termed Polianie, their speech was still Slavic. They were known as Polianie, because they lived in the fields, but they still had the same Slavic language.

Unsurprisingly, pol'- meant 'field' in Common Slavic. The ethnonym Polanie survives in the name of modern Poland, though there seem to be both West Slavic Polianie and East Slavic Polianie that Nestor mentions. The West Slavic Polianie are mentioned in a list along with Mazovians and Pomorians as part of the "Liakhs", a group of Slavic tribes that we can probably equate with the linguistic ancestors of the modern Lechitic languages. So, here, we see a clear recognition of linguistic kinship between the Rus' and early West Slavs.

The second kind of Polianie Nestor later equates with the Rus', and these Polianie receive St Andrew's mission to the Slavs along the Dnieper, according to the Chronicle the first such mission to the Slavs. Nestor describes the Polianie who would become the Rus' as "mild and peaceful" (important Christian traits), and notes that even before St. Andrew's mission they had marriage customs. The neighboring Slavic tribes are the target of some mockery, though, especially the Viatichians, who at the time of writing were still pagan. It seems, then, that though Nestor was very much aware of some kind of linguistic link, confessional status was also a very important component of identity.