Table 1. Number of twins, siblings, parents and spouses and their mean age (standard deviation) and age range.
| N | Mean age (SD) | Age range | |
| Twins | |||
| Monozygotic males | 757 | ||
| Dizygotic males | 389 | ||
| Monozygotic females | 1,894 | ||
| Dizygotic females | 932 | ||
| Dizygotic opposite sex males | 417 | ||
| Dizygotic opposite sex females | 628 | ||
| Total | 5,017 | 33.7 (11.0) | 18–86 |
| Siblings | |||
| Brother | 472 | ||
| Sister | 794 | ||
| Total | 1,266 | 38.1 (12.3) | 18–90 |
| Parents | |||
| Fathers | 1,357 | ||
| Mothers | 1,707 | ||
| Total | 3,064 | 57.5 (6.5) | 34–87 |
| Spouses | |||
| Male spouses | 595 | ||
| Female spouses | 344 | ||
| Total | 939 | 38.0 (12.2) | 19–80 |