The Wyndermyre Memoirs by CeDany

CeDany has a web presence from where you can download a fantasy book series, The Wyndermyre Memoirs, featuring a family from a different realm.
That star's system and its calendrical similarities and differences to Earth's are outlined, and (at least some of) the residents on that planet appear to have more in common with the Ancient Greek or Scandinavian gods than with us mere mortals. The fantasy elements feature something of a genealogy.

Further background is detailed, linking our own blood types (A, AB, O, etc) to what could closely align with a clever "Twelve Tribes of Israel"-type concept.
It doesn't explain why we have blood types, but the assignation of a deity and descendants to each blood type is a nice touch.
The series is told from multiple perspectives, with an epistolary form that stretches back half a millennium, featuring raids on villages from a slightly prochronistic "Viking" class underpinning a modern-day setting featuring a college-bound heiress.
The laws of the period are invoked for making and staking claims on women, and full moon dates cited with an exactitude that suggests what goes on above has something to do what goes on below.
There's lots of entertaining back-story and mythos revealed in this epic, and the work appears to be inspired by the legends of multiple cultures, primarily European.
You can get the books free here.