[Phaala Deepika, Ch. 3]
6. The Saptaanshs or the 1/7th portion are in the case of an odd sign, counted regularly from the sign itself. In the case of an even sign, they are counted from 7th sign onwards.

[Kalyana Varmas Saravali, Ch. 3]
16. Lords of Saptaanshs. The Saptaanshs for the 12 Rasis from Aries onwards are, respectively, counted from Aries, Scorpio, Gemini, Capricorn, Leo, Pisces, Libra, Taurus, Sagittarius, Cancer, Aquarius and Virgo. The Lords thereof are those, in whose Rasis they fall.

Paraashar only gives 'sons and grandsons' (meaning progeny in general) as theme for Saptaansh, but as Navaansh Saptaanshs have far more significations - Navaansh are designated for use for 'spouse' by Paraashara and surely Navaansh indicate far more than only spouse and marriage.

Saravali states that 'regarding effects for various other divisions not explained, the effects related to Saptaanshs will apply.' This hints at the general importance of Saptaanshs (even more than Dashaansh), like Navaansh and DwaDashaansh.

Saravali further explains that 'courage, wealth and fame' are the consequences of a planet occupying its own Saptaansh, e.g. Sun in Leo Saptaansh is auspicious for all Leo themes and supports fame and success to all natural and functional significations of the Sun (of course all other Avasthas - as always - are applicable).

Saptaanshs are related to the Bhaav Karaka of the 7th Bhaav, Venus.

All indications from 7th Bhaav can be derived from Graha's placements in Saptaansh:
(a) activities in outer world with other people to fulfill one's desires and wishes
(b) relating oneself to environment, outer world, surroundings
(c) marriage, spouse, partners of all kings (also business partners)
(d) passions, sexuality
(e) journeys to foreign lands

[Bhrigu Sootras, Ch. 1]
House of union or earthly ties, legal bondage, partner in life (wife or husband), partner in business, conjugal life, influence in foreign countries and reputation achieved there, sexual life, marital relations, danger to life, Maarak Sthaana (house of death).

The calculation of Saptaansh Varg is 7 = 3 + 4: desires and activities (3rd Bhaav) in combination with our inner self, emotions, mind and mentality (4th Bhaav), resulting in manifesting and fulfilling these desires in our surroundings, personal environment and outer world in general. Marriage and sexuality is just one (but very important) aspect of these desires and our activities resulting thereof.

Saptaansh show all results of our relationships with our own world and - as a particular part of these relationships in general - of our partnerships or marriage. The main result of our partnership or marriage is generally progeny, but there can be quite different results as well. Grahas posited in Saptaanshs tell this story - which social effect they will have in our life.

Therefore Saptaanshs are indicating our social power and success, Dashaansh our individual power and success. The link between Grahas in Saptaanshs and DwaDashaansh exists in their social attitude - both start with the same Amsa sign as the Rashi they are placed in. Saravali writes: 'One becomes devout and helpful, if a planet is in its own Dvadashaamsa. ' This applies for Saptaanshs as well.

Saptaansh are - with regard to Dashaansh (D-10) - sub-estimated, and the placement in the Sapta Varg Scheme (where Dasamsa Varg is not included) proves the true importance of Saptaansh Varg.