As other commenters mentioned, the word genetic did already exist

This quote essentially uses "genetic connection" in reference to what we now call "blood related"

But the thing that actually is crazy about Darwin in terms of genes is that he discovered natural selection, a phenomenon about genes, without knowing genes existed.

Evolution had be hypothesized / theorized for a long time before Darwin, it dates back to 495–35 BCE. Much of the terms he used in that book are not terms now, but were terms already developed by other evolutionary scientists prior to him using them. "genetic connection" had been used already to mean descended from the same being. The major evolutionist before Darwin was Lamarck, who coined and described many of the terms like that and described them quite accurately. Lamarck knew about inheritance and acquired traits already and did refer to this using terms like genetics, so Darwin did have that information.

Darwin did notice patterns that he assumed must be due to traits the animals must have in order for the patterns to be happening. He usually used the term "undergoing modification". He said many things that were about genes and inheritance without using modern terms before model, he definitely understood and noticed genetic patterns without figuring out what was causing them.