To give a Heesch/Schrum descendant who is browsing this information an example of how they would be related to me...
Here is a generational breakdown to simplify how the Grau & Heesch families are connected

Detlev and Elsabe Grau children: Johann, Jochim, Maria, Detlef, and Gottlieb

Siblings: Maria Grau (John Heesch) - Detlef Grau (Sophia Sachleben)
1st Cousins: Heinrich Heesch (Veeden Sievers) - August Grau (Maria Hansen)
2nd Cousins: Emma Heesch (John Schrum) - Ida Grau (August Kusel)
3rd Cousins: Elroy Schrum (Darlene Boeck) - Amos Kusel (Dorothy Ehrichs)
4th Cousins: Stanley Schrum - David Kusel