A recent TUC study suggests working fathers get 21% wage bonus

It is suggested that in Britain a father of two earns 9% more than those of just one child.
The reasons for this most likely due to the hours worked.  It is believed through statistics, full time working fathers worked on average half an hour each week longer than those without children.
In turn, it states full time working mothers earned 11% less than their childless colleagues.  Although, the survey did suggest that whilst working mothers received less, it was also found that women who had their children 33 or over were paid 12% more as they had already developed their skills and were more likely to return to full time work after maternity leave.