Species vs Alien
Connection:
Both are sexually aggressive villains from sci-fi horror movies with the mission to increase the population of their species Sil's and Xenomorph's respectively) and replace the race of whatever planet they're on
Both were also created by H.R. Giger
Both their race go through different stages of their life cycle
Both have a very rapid growth rate and their species burst out of their parent/host's chests in different (Sil giving birth by opening her chest cavity whereas the Chestbursters kills their host upon birth)
Both have methods of killing involving deadly weapons in their mouths (Sil's tentacle mouth and the Xenomorph possessing an inner jaw)
Both seem to have a telepathic method of communicating with their own kind
Both have different variations of their species (Sil's Species race having multiple generations such as Eve, Sara, Miranda Hollander, Amelia and males such as Patrick Ross and Yosef, whereas Xenomorphs has Newborn, Deacon, Neomorphs, the Predalien, Crocodile Alien, etc.)
Both were created by a higher alien race (Sil's unnamed true Species race and Engineers respectively)