Table II.
Description of family structures
| Subject type | Number of individuals |
|---|---|
| Monozygotic twins (data from one twin was missing for six pairs) | 220 |
| Dizygotic twins (data from one twin was missing for two pairs) | 96 |
| Single‐birth siblings of twins | |
| One single‐birth sibling in family | 34 |
| Two or more single‐birth siblings in family | 22 |
| Single‐birth sibling groups from families without twins | |
| Siblings in pairs | 68 |
| Siblings in trios | 27 |
| Siblings in quartets | 16 |
| Siblings in quintet | 5 |
| Single birth individuals without siblings | 112 |
| Total | 600 |