Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 8 · Marriage
विवाहः
प्रत्युद्वाहो नैव कार्यो नैकस्मै दुहितृद्वयम् ।न चैकजन्ययोः पुंसोरेकजन्ये तु कन्यके ॥ ५१७ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 56, verse 517.
No exchange wedding should be done. Not two daughters to one man. Not two men born of the same mother to two girls born of the same mother.
Simple meaning: Do not do an exchange wedding. Do not give two daughters to one man.
नैवं कदाचिदुद्वाहो नैकदा मुंडनद्वयम् ।
Some weddings and rites must not be done twice together. Birth at certain times may risk a parent's life.
आत्मानं संध्ययोर्हंति नास्ति गंडे विपर्ययः ।
A twilight birth may risk the child's own life. A Moola birth may risk the father-in-law's life.
तदंत्यपादजो नैव तथाश्लेषाद्यपादजः ।
A boy born in Jyeshtha's last quarter may put an elder sibling at risk. Mula's last quarter does not.