Jacob, Rachel, and Leah

What I really don't understand is why women back in their time thought that their slaves' children were their children. I mean, I can understand as far as "Well, it's my slave, I own her, she's mine, so if my husband has sex with her it's okay." [I just don't agree with it, but I understand it.] *sighs* It just seems sick and wrong. I mean, if (***if***) I had a husband and a maid working in my household, I wouldn't want to walk up to the maid and say, "Hey, I would like you to have sex with my husband so that I can legally call your children mine." That's just a major wrong thing to do in today's world. Maybe that's why I don't understand it, because it was so long ago.