Two people, two birth charts. Birth date, time and place give each person’s rising sign and houses, and a planet-by-planet comparison of the two charts.
Planet positions from Astronomy Engine: apparent positions on the tropical zodiac, checked against a published professional chart to within a quarter of an arcminute. Birth time is turned into world time with your browser’s own time-zone history, which knows about daylight saving back through the 20th century. Before 1970 some places’ records are approximate, and older births may have been recorded in local mean time. Placidus and Koch fall back to Porphyry above about 66° latitude, and say so. Davison chart: the midpoint of the two births in time and in place.
Sun-sign element relationship 40, Chinese animal triad 25, numerology life-path resonance 20, modality mix 15. Summed and normalised to 100. It is a rule of thumb with the rules published, not a measurement. No birth time means no rising sign, no houses and no aspects: for those, use the full chart comparison.