Complex sentence: They live in Khyber Pakhtunkhwa, Pakistan and Balochistan Province of Pakistan: some of them have migrated to Karachi city and very small portion of the population is living in Lower Punjab.
Split into simpler sentences: They live in Khyber Pakhtunkhwa, Pakistan and Balochistan Province of Pakistan. Some of them have migrated to Karachi city, and a very small portion of the population is living in Lower Punjab.