Here are the matched sentences with their extensions:

1. **My next-door neighbours, Paul and Sophie, are a married couple with two young children.**
- **a. we were a traditional extended family.**

2. **It's important for young people to have appropriate role models.**
- **b. this means returning to work after childbirth can be difficult for some mothers.**

3. **Some parents can be over-protective.**
- **c. the sibling rivalry can result in small fights and arguments.**

4. **The average family size is becoming smaller.**
- **d. luckily they had support from other single-parent families.**

5. **My parents weren't very strict with me when I was young.**
- **e. most brothers and sisters experience some degree of jealousy and competition.**

6. **Childcare can be very expensive.**
- **f. however, they are a typical nuclear family.**

7. **My friend Sally was raised by foster parents who later adopted her.**
- **g. and her mother was unable to look after her.**

8. **After he was widowed, Phil brought up his daughters on his own.**
- **h. they do not allow their children to take risks and become independent.**

9. **I grew up in a house with my parents, grandparents and an aunt and uncle.**
- **i. in fact, they were very lenient and rarely punished me.**

10. **In some countries, the birth rate has decreased recently.**
- **j. this is a big concern for many governments.**

Feel free to ask for any more assistance!