Had Friedrich Doenitz brother van Karl Doenitz ouwn children?

Friedrich doenitz had at least 1 son i know off and his name is peter wallis who lives in Bristol England. I know peter has a sister but i don't know her name. peter in turn also has a son i know of who goes by the name of Simon and father and son both work for the company D20 ( A groundworking company )

I hope this information helps