One twin can be two months older than the other.
Here is a common scientific myth that isn’t actually a myth. A Romanian woman gave birth to a set of twins seven weeks apart. After her first child was born, she immediately stopped having contractions. The doctors advised that she keep the other baby inside to develop a little longer. She carried her second child for seven more weeks before delivering by a C-section.
The Earth is called Telleus and/or Terra after both greek and roman gods.