Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
एकराशौ पृथग्धिष्ण्ये दंपत्योः पाणिपीडनम् ।उत्तमं मध्यमं भिन्नं राश्यैकत्वं ययोस्तयोः ॥ ४९७ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 497.
If the couple share one sign but have different stars, the wedding is best. It is middling for two whose signs differ but whose star is one.
Simple meaning: Same sign, different stars is best for a wedding. Same star, different signs is middling.
एकर्क्षे त्वेकराशौ हि विवाहः प्राणहानिदः ।
The same star and sign may put life at risk. His star within nine of hers is not good.
द्वितीये मध्यमं श्रेष्ठं तृतीये नवके नृभम् ।
Middle if the man's star is in the second nine, best in the third. A star group is named.
इति मर्त्यगणे ज्ञेयः स्यादमर्त्यगणः परः ।
That was the human group. The god group is Shravana, Punarvasu, Hasta, Swati, Revati, Anuradha, Ashvini, Pushya and Mrigashira.