能不能这样说讷

不能，如果你想说的是我是我家唯一的小孩。
应该用i'm the only child of the family.
single是单身。。

独生子女用the only child
the only child in one's family

single ['siŋgl]
adj. 单身的,单纯的,单一的
1.The entire content of a book will be located on a single silicon chip.
整本书的内容只用一片硅芯片就可以装下。
2.The unification of Italy resulted in a single country instead of several kingdoms.
意大利统一的结果是出现了一个国家，而 不是好几个王国。