Xenomorphs are shapeshifters. They can look like anything and anyone of the proper shape and mass. They are born resembling the young of whatever shape the mother is wearing them. Xenomorphs keep their true nature a secret. Normally not hostile they will be aggressive if they are caught in the act of shapeshifting.
The homeworld of the Xenomorphs is not known and most about them is mysterious. They normally do not take part in galactic politics.
Source: GURPS Aliens