Being an Alpha born means you are superior to the Omega and Beta, but the Alpha will only mate an Omega.
Being a Beta born means you are somewhat superior to the Omega but lower than the Alpha. These wolves are the middle ground and are more logical in way of thinking. They will only mate with other Betas.
Being an Omega born means you are lower in rank to the Alpha and Beta, but the Omega will only mate with an Alpha and, on most occasions regardless of gender, bear the Alpha's offspring.