It sounds like what you’ve heard is a mixed up account of the dominant modern position among Roman Catholics on extraterrestrial life. The modern view is broadly that while extraterrestrial life may exist, it’s not clear how this life would fit into the history of salvation, since they wouldn’t be descendants of Adam. So it is not prima facie clear that they would have fallen like humanity or require religion, like humanity in its fallen state, to mediate their relationship with God. For a famous example, you can look up the comments of then director of the Vatican Observatory José Gabriel Funes, that we shouldn’t assume that extraterrestrial life required redeption. (Here is the original Italian, there are a bunch of translation floating about, including a number linked from his wikipedia page if you’re intersted.)

This position goes back to the Fathers, who discussed the same sort of question about the so called “monstrous” races that were, throughout antiquity, believed to live at the fringes of the inhabitable world. And indeed, Augustine gives a similarly non-commital answer on the status of these quasi-humans:

It is also asked whether we are to believe that certain monstrous races of men, spoken of in secular history, have sprung from Noah's sons, or rather, I should say, from that one man from whom they themselves were descended.

[…]

Wherefore, to conclude this question cautiously and guardedly, either these things which have been told of some races have no existence at all; or if they do exist, they are not human races; or if they are human, they are descended from Adam. (City of God, 16.8)

And indeed, in this discussion, Augustine suggests, as you note here, that God may have decided to create:

But supposing they are men of whom these marvels are recorded, what if God has seen fit to create some races in this way, that we might not suppose that the monstrous births which appear among ourselves are the failures of that wisdom whereby He fashions the human nature, as we speak of the failure of a less perfect workman?

This question saw continued discussion through the Middle Ages, as in the famous 9th century Epistola de Cynocephalis by Ratramnus of Corbei, in which he argues that the Cynocephali (humans with dog heads) are indeed human. Just to give one other prominent example, in his highly influential encyclopedia, Honorius Augustodunensis includes a chapter on Monsters and on Beasts right after his discussion of India (the region of the world, followed by Ethiopia, which is especially associated with strange creatures) which he begins by noting that:

There are certain monsters there, which some consider humans and others consider animals….

Sunt ibi quedam monstra que quidam hominibus quidam ascribitur bestiis… (Imago Mundi 1.11) [N.b. I’m inclined to follow C and E here and read ascribunt rather than ascribitur.]

But as to the question of extraterrestrial life, or rather as they discussed it the question of other worlds, the dominant view was negative. This goes back to the dominant ancient views on the structure of the cosmos. To account for the forces of gravity as we experience them on earth, and earth’s sphereicality, ancient authors tended to posit a cosmic centre, towards which heavy bodies (like earth and water) were naturally inclined and the converse for light bodies (like fire and air). (I’ve written about this at length before here.) As a result, besides the Atomists who denied this entire picture and argued for a plurality of inhabited worlds (see Lucretius, 2, l.991ff.), the dominant view was that there was only one world. This view is examplified by Aristotle’s arguments in De Caelo 1.9 that there couldn’t be other worlds because our world contains the sum total of perceptable matter that exists. Indeed, this notion of a cosmic centre and the associated concepts of natural and violent motion grounds a very simply argument for the incompatbility of this framwork with the existence of other worlds. For example, here is Micael Scot’s (1175-c.1232) version in his commentary on Sacrobosco’s De Sphaera (a standard late medieval cosmological textbook):

[Assuming there was another world] it would follow necessarily that the earth of another world would be moved toward the middle [or center] of this world, or conversely. Ans similarly, the first of another world would be moved toward the upper part of this world, or conversely… (as cited in Grant, Planets, Stars, and Orbs, 154)

And this is obviously impossible as between the two centres nothing would have a natural place.

Nevertheless, this was a standard topic of discussion in the later medieval universities. (For example, Aquinas discusses this inter alia in Summa theologica 1.47.3.) So much so, in fact, that the proposition: “That the first cause [God] could not make several worlds.” was one of the propositions (#34) condemed by the Bishop of Paris, Etienne Tempier, in the famous condemnations of 1277. As a result, while before this the discussion is largely based around giving reasons why God didn’t or couldn’t create multiple worlds, after 1277 there is a wider discussion of how such a multiplication of worlds could occur. For example, Nicolas Oresme argues that there could be smaller worlds within our world, or a bigger one within which our world is set. (Kinda like the plot of Men in Black 1… is this even a meaningful reference anymore?) And this solves the problem that Scot points out, because given their concentric arrangement, they can all share the same centre, like a set of nesting dolls.

But we can probably count on one hand the number of authors who argued for this as more than a merely possible state of affairs, and they mostly come at the very end of the Middle Ages in either the fifteenth or sixteenth century. Grant suggests that John Major (not the ex-British prime minister, this one died in 1550) is the only Scholastic author to argue for a plurality of worlds. But the other two famous examples are Giordano Bruno and Nicholas of Cusa.

And it is with this last figure that we find one of the only examples of a medieval author arguing about extraterrestrial life. He suggests that since life on earth is tailored to earths nature, shouldn’t we assume that life on other stars would be tailored to their natures as well? So while humans are earthy, moon people would be water and sun people would be fiery:

By comparison, here on earth it happens that animals of one species—[animals] which constitute one specific region, so to speak—are united together; and because of the common specific region, they mutually share those things which belong to their region; they neither concern themselves about other [regions] nor apprehend truly anything regarding them. For example, an animal of one species cannot grasp the thought which [an animal] of another [species] expresses through vocal signs—except for a superficial grasping in the case of a very few signs, and even then [only] after long experience and only conjecturally. But we are able to know disproportionally less about the inhabitants of another region. We surmise that in the solar region there are inhabitants which are more solar, brilliant, illustrious, and intellectual—being even more spiritlike than [those] on the moon, where [the inhabitants] are more moonlike, and than [those] on the earth, [where they are] more material and more solidified. Thus, [we surmise], these intellectual solar natures are mostly in a state of actuality and scarcely in a state of potentiality; but the terrestrial [natures] are mostly in potentiality and scarcely in actuality; lunar [natures] fluctuate between [solar and terrestrial natures]. We believe this on the basis of the fiery influence of the sun and on the basis of the watery and aerial influence of the moon and the weighty material influence of the earth. In like manner, we surmise that none of the other regions of the stars are empty of inhabitants— as if there were as many particular mondial parts of the one universe as there are stars, of which there is no number. (De docta ignorantia, 2.12)

With the breakdown of the Aristotelean cosmos (or rather as the terms by which cosmology was discussed broke away from Aristotelean categories) and particularly with the return of Atomism, through the renewed popularity of Lucretius and others, we find this sort of thing cropping up more commonly in early modern sources. Thus we find Kant speculating about the nature of extraterrestrial life in the appendix to his first major work, the Universal Natural History and Theory of the Heavens, where he likewise argues about how life would be tailored to the condition of different planets. And he suggests, for example, in terms that are surprisingly similar to those of Nicolas 300 years earlier that:

The inhabitants of Venus, whose cruder structure and sluggishness in the elements of their formation require a stronger solar influence, would in a cooler celestial region freeze and die from a lack of vitality. In the same way, the body of an inhabitant of Jupiter would have to consist of far lighter and more volatile material, so that the very small motion which the sun can induce at this distance away could move these machines just as powerfully as it does in the lower regions.