No. Slaves were never family. Even slaves who were forced to bear the slaveowners children saw those children abused and sold or were themselves further abused and sold. That statement seems to be commonly used to ease a slave holders mind while justifying the holding of slaves. I believe it is said in an attempt to minimize the "sinful" nature of slavery and offer a clear conscience to the slave owner. No, I don't think Margot believes this either. I don't think she is convinced of it, however, I do think it is a means of providing some comfort from a constant state of worry in a situation she can do little to free herself from. I don't think she convinced herself of this because doing so would undermine her survival and leave her unprepared for any action she needed to take to protect her from further abuse or being sold into an unknown situation.