What is covered?
For members of the same household, one contract is usually sufficient. In family insurance, all unmarried children are generally co-insured if they are still in education or military/civil service.
Co-insurance is also possible if unemployment follows education. The same protection applies to unmarried couples, often including same-sex couples.
If a couple moves in together, both can be insured under one contract. The longest-standing contract is continued, and the "younger" policy can be cancelled without notice. However, there is no liability between joint contracts. So, if the new housemate damages the expensive stereo system, the insurance will not cover it. Such double insurance should be avoided.
There are special rates for singles, young people up to 25, and seniors over 60. However, no additional persons can be co-insured, as the coverage amounts are sometimes lower or include more exclusions.