婴儿弟弟怎么说用英语

In English, you can refer to your baby brother as "my baby brother" or simply "my brother." You can also say "my younger brother" if you have an older sibling. Some other options include "my little brother" or "my sibling."

For example, you could say:

"I have a new baby brother."
"Meet my little brother."
"My younger brother is six months old."
"I have a baby brother and an older sister."