Familienstatus

Familie (“family”) +‎ Status (“state, status”). Possibly, it is a loan translation of English family status (“position within the family”). The sense “marital status” would then have developed by interpreting the word as synonymous with Familienstand (“marital status”, literally “family state”).

Familienstatus m (genitive Familienstatus, plural Familienstatus or Familienstatusse)

1. (sociology) family status (one’s position within the family, e.g. adult child living outside of the parental home, etc.)
2. (sociology) marital status (the fact of one’s being unmarried, married, divorced, or widowed); outside of official use sometimes including information about children, unmarried life partners, etc.

• (marital status): Familienstand (more common)