what does douglass believe are some of the worse consequences of master's siring of children on their slaves?

Douglass believed that the worse consequences of masters' siring children on their slaves would be the fact that the progeny of the master would probably face mistreatment by the master's wife, or that the slave child's brother (legitimate) might beat him. The "white" brother could legally impose any punishment he desired because of the color of the slave brother's skin.