co-twin

例句：

1. 1.They had a co-twin who was born with them.
   他们有一个与他们同时出生的双胞胎。
2. 2. The co-twins were raised together and became very close friends.
   这对双胞胎一起长大，成为了非常亲密的朋友。
3. 3.Co-twins are often genetically identical, despite being born at different times.
   尽管出生时间不同，双胞胎往往基因相同。