Most of us would like something about ourselves or our lives to be different, but how easy is it to actually change?

Drs Chris and Xand van Tulleken are looking at whether people can change and how they do it. Exactly how much of any aspect of personality is genetic destiny and how much are we shaped by the world around us?

Chris wants to be a better doctor, friend, husband and father. But most urgently he wants to be a better brother, and is determined to improve his relationship with Xand. They’re best friends and talk to each other every day, but they are also business partners who find it very hard to work together without having a visceral row.

Chris wants to change how he relates to his brother and believes it is possible, but Xand is less convinced that we can or that he needs to change. In this series, Chris confronts that pessimism

In episode 1 - The Twin Effect - Dr Clare Llewellyn explains why we should all care about twin studies and the importance of understanding the impact of genetics vs environment on our development. Chris and Xand meet identical twins Mia and Alexandra who were separated at birth. They reflect on their twin dynamic through the years - what has it meant for their development and can they change the dynamic they have now?Presented by Drs Chris and Xand van TullekenProduced by Hester Cant and Alexandra QuinnSeries Editor Jo RowntreeA Loftus Media and van Tulleken Brothers Ltd production for BBC Radio 4