If two people are twins, they have the same mother and were born on the same day.

Twin is used to describe a pair of things that look the same and are close together.

Twin is used to describe two things or ideas that are similar or connected in some way.

When a place or organization in one country is twinned with a place or organization in another country, a special relationship is formally established between them.

Twin towns or cities are twinned with each other.