Raised among adults
The description fits anyone whose nearest sibling is six or more years away, not only those with no siblings at all. Without a brother or sister to argue with, an only child often treats parents as peers: they debate with them, confide in them, and pick up a lot of their values. As adults they tend to be at ease with bosses and older people, confident in their own opinions, and ambitious.
The same setup can breed perfectionism. When the only standard in the house was adult-sized, some onlies put off starting a task because it has to be done perfectly. Others become worriers or pleasers, very aware of how their actions land on people. A partner can help by praising the finished draft, not the perfect one that never got started, and by treating a mistake as ordinary rather than a crisis.
The myths, and what holds up
The old picture of only children as lonely and spoiled hasn’t held up well. Studies comparing them with children who have siblings find few lasting differences, and some find onlies doing slightly better at school. So read what follows as tendencies, not a profile.
Dating an only child
Expect a strong bond with their parents. An only child may complain about their parents at length, but that right is theirs: joining in tends to go badly. They may also want more time alone than a partner from a big family expects, and need to hear that a quiet evening apart isn’t a problem. Some lean on their parents for help well into adulthood, which is worth talking about openly if you’re building a home together. Holidays can be a sore point too: with no siblings to share the visits, an only child may feel every Thanksgiving belongs to their parents.
Only children as partners for eldest, middle and youngest
Two only children, or an only with a firstborn, are often productive and evenly matched, and can both be sharp critics and sensitive receivers of criticism. Clear areas of responsibility, and trust in each other’s judgment, help.
With a middle child, the only often takes the lead and the middle is happy to let them. The only should keep reassuring; the middle should speak up early.
With a youngest child, the only brings follow-through and the youngest brings play, which many couples find a good balance. The birth order overview explains the theory behind these pairings.