Manu[ref]icchayāanyonyasanyogaḥ kanyāyāśca varasya ca |
gāndharvaḥ sa tu vijñeyo maithunyaḥ kāmasambhavaḥ || MS iii.32[/ref] describes the Gāndharva vivāha as the voluntary union between the bride and the groom leading to the sexual act being overcome by sexual desire. This is the love marriage of the modern world.
It is pure and simple physical attraction and love that leads to the sexual union between a couple and there is no exchange of any kind nor any agreement or ceremony. Even a one-night stand can be counted as this kind of a marriage where the couple are overcome with lust (or love).
Sometimes this can extend into a marriage ceremony with or without the participation of parents but is deemed to lead to the separation or distancing of the parents of both the couples. It is blameworthy as the marriage act is not based on a sense of duty or dharma towards either the universe, society or family and is a very animal instinct based decision.
Its greatest flaw is that this love or rather lust, is skin deep and shall normally wear away in about a decade or two unless it is earlier and it is also possible that each of the couples may get attracted to another partner due to the same lust or strong sexual desire.
Yet this is the preferred form of marriage among the young at heart who are struck by the five arrows of Kāmadeva, the god of love. The challenge in front of this couple is convert their lust (ratī) to pure love (prīti). Normally, śāstra teaches that when a couple confess their attraction to parents, then ‘guṇa-score’ matching of horoscopes (36 point system) is irrelevant as they have already found themselves attractive. Yet their horoscopes need to be matches for ṣaḍāṣṭaka and other such doṣa mentioned in the purāṇa.
Gandharva vivāha has some very strong advantages as it is ruled by Venus, the natural significator for marriage. The word गन्धर्व (gandharva) refers to a class of beings designated as heavenly (divvyā~)[ref]RV. Ix.86.36[/ref] and also called Viśvāvasu[ref]RV. x.85.21-22[/ref] and Vāyu-keśa[ref]RV. iii.38.6[/ref]. They inhabitat the sky (ākāśa or svarga loka) as well as antarikṣa (the region of the air) and ākāśa-ganga (the heavenly waters) [ref]RV. i.22.14 ; viii.77.5 ; ix.85.12 ; 86.36 ; x.10.4 AV. ii.2.3[/ref].
The special duty of the gandharva is to guard the heavenly Soma [ref]RV. ix.83.4 and 85.12[/ref] which is the elixir of life thereby alluding to the power of rejuvenation (mṛtyuṅjaya mantra) obtained by Śukrācārya (Venus in jyotiṣa). Gandharva vivāha is actually very healthy and heals the body and mind. The heavenly Gandharva is supposed to be a good physician, because the Soma is considered as the best medicine. It rejuvenates by bringing great joy of being loved, to the consciousness. It is truly divine in its purest sense. Even the devas obtain soma through the intervention of the gandharva [ref]RV. AV. vii.73.3; cf. RV. i.22.14[/ref] whereas it is obtained for the human race by Indra-deva [ref]represented as the adi-devatā of putra-kāraka Jupiter implying that progeny can comes naturally through copulation[/ref], who conquers the Gandharva and takes it by force [ref]RV. viii.1.11 and 77.5[/ref]. Apsara are the wives of the Gandharvas.