The Lifelines cohort consists of many family relationships. During the inclusion into Lifelines, participants were asked if they had any family members who would be interested in joining the cohort. As a result Lifelines is one of the largest 3 generation cohorts available.

The basis of the family relations data within Lifelines consists of information from the municipal registries (Basisregistratie Personen (BRP)). Based on this information, researchers from the UGLI-consortium have optimized the family relations using recoded surname data (for privacy purposes) and data from questionnaires (Family composition). The process of this optimization has been documented and can be found here: Family relations reconstruction.

These optimized family relations were then verified by the UGLI-consortium using available genetic data. The most recent version of the family relations data (sec_family_relations_v3.1; July 2023) has been verified by using genetic data from GWAS (CytoSNP), UGLI 1 (GSA), and UGLI 2 (Affymetrix). More detailed information on this process can be found in the quality control document of UGLI2-Affymetrix: QC_report_UGLI2_(release_1)-v1.pdf, page 6 - 9, section 6b and in the readme of the familyrelations.

Note that the family relations file does not provide information on whether a family member lives in the same house. Information on postal code 4 is available in your data by default and data on household composition can be requested through our catalogue.

The family relations file is not available through our catelogue, but can be requested by sending an e-mail to data@lifelines.nl (this does not apply to UGLI consortium cluster users, who can already find the file in pheno_lifelines). If you do not already have access to the family relation file, please also complete our amendment form.

The data in sec_family_relations_v3.1 consists of 5 columns:

• Participant identifiers
• Family id
• Father identifier
• Mother identifier
• Gender
• Partner identifier

The identifiers can be used to pair the family data to other phenotypic and genotypic data. The same participant identifier can also be found in the column for father or mother and partner. In which column the identifier can be found, depends on the participant's family size and if they are, for example, both a child and a parent. With the use of self reported data on family members like birthdays of parents and siblings, family members shared between siblings could be derived. These are family members that do not participate in Lifelines. Other than the family member connection, we do not have any other information on these persons. These derived family members have received a unique identifier (an S-number, i.e. S1031206). This identifier cannot be used to pair the data to other Lifelines data. An example is when two siblings have indicated to have the same parent; the (non-participating) parent has then received an S-number. The family id is used to identify participants that are part of the same family. Couples who share a household, but don't have children, also receive a family id. This provides the opportunity to work on research involving environmental factors. Note that partner information is based on baseline data.