Brihajjataka 4.14

4.14

yugme candra sitau tathā oja bhavane syur jña āra jīva udayā lagna indū nṛ nirīkṣitau ca samagau yugmeṣu vā prāṇinaḥ/
kuryur te mithunaṃ graha udaya gatān dvy aṅga aṃśakān paśyati sva aṃśe jñe tritayaṃ jñaga aṃśaka vaśād yugmaṃ tv amiśraiḥ samam//(śā vi)

When the Moon and Venus are in an even sign, and Mercury, Mars, Jupiter, and the ascendant are in an odd sign; or when the ascendant and Moon are aspected by a male [planet] and situated in even signs; or when the living beings are in even [signs], / they cause twins. When [a planet] aspects dual degrees occupying the planetary ascendant while Mercury is in its own navāṃśa, triplets [are born]; triplets are equal [in sex] according to the navāṃśas occupied by Mercury, but through unmixed [influences].