Create a single male Sim. Give him one child. Starve the child to the point that the social worker arrives to pick him or her up. Make sure that the father is home and not busy. The social worker should lecture the father. This will cause a relationship with her. Have the man call her. Once you get their relationship high enough that you can invite her over, do so. Note that you are not able to enter build and buy mode. If you get them married, she will have the first name "Social" and a last name of the male Sim. A new social worker will replace the old one, usually with a change of hair color being the only difference.
