twin: one of two children born at the same time to the same mother
Ex: She's expecting twins.
The twins are now eight months old.
Ok, let say a woman has twins at her first birth (ie, there are only 2 children)
So, we say "I have 2 twins" or "I have twins"?
And , what if she has twins at her second birth.
Do we say "2 pairs of twins"?