Dear Sir,
With all due respect, let me pl elaborate. Others on this forum may pl correct my understanding.
Kula Deivam or Kula Devata is the God of the family/Clan, hence the most important to worship. Pl refer URL below, where a very large section of people in South & North India (Both Brahmins & NBs) worship Kula devata.
Further Kula Devata can be derived through the 2nd House of the Horoscope which is rooted strongly in Vedic Astrology !. I am not an expert on Astrology, but have some basic understanding.
: kamakoti.org
Reference to Shiva Puja from Skanda Purana
The worship commences with Mantras addressing the very first Deity Ganesha with ‘Om Gam Ganesaya namah’ followed by two others, with Om Kshey Kshetra Palaaya namah, and Om Gum Gurubhyo namah and dedicates the Puja material to ‘Akash’ (Sky). Later on, he worships in the following order directed towards to four directions viz. Kula Devatha, Nandi, Mahaakaal, and Dhatha- Vidhata with the mantras: Om Kum Kula Devathaya namah, Om nam Nandiney namah, Om Mahaakaalaya namah and Om Dhaam Dhaatrey Vidhaatrey namah.
Kuladevata - Wikipedia, the free encyclopedia
Kuladevata (kula-dèvatā) or Kuladevi, also known as Kuladev and Kuladaivat, stands for "family deity, that is either a god or a goddess" within Hinduism, as distinct from personal ishta-devata and village deities. This is similar to Tutelary deity worshiped in other parts of world.
Kuldevi mantra : ;;Om Sri Kuldevyai Namah.
Worship of the kul-devata or kul-devi is considered to be of utmost importance. The Kul-devata is the guardian of the family, of the lineage. Ancestors of the family have worshipped the deity and there is a bond between the family and the deity. Hence such worship bears fruits early. Worship of the kuldevata is said to appease the deity who is the sole protector of the family. One who worships his/her family deity is said to be protected by the deity in times of calamity.
Cheers,
JK