why would my girlfriends x be the 7th? i'm asking about her and him so wouldn't she be the 7th?
Selecting the correct Houses/Significators depends upon whether or not you have permission to ask the Question.
You always have permission to ask Questions that are directly related to you. Third Parties, by definition, have no direct relationship to you and so you don't have permission to ask Questions about 3rd Parties (unless the 3rd Party comes to you and says, "Ask a Question about me.")
If that sounds confusing, it is supposed to be. It's a built in "Check & Balance" designed to keep people from abusing Horary and knowing things they have no business of knowing because that tends to lead to extreme sorrow and grief.
Even when someone is directly related to you, like your girlfriend, the correct House/Significator depends on permission.
If you suspect your girlfriend is pregnant, and you ask that Question, and you don't have permission, she is the 7th House, but if you tells you, "Ask an astrologer if I am pregnant" then you have permission and she effectively is the "true Querent" and she is the 1st House, even though she is your girlfriend.
It's also why people should consult with an astrologer because as Bonatti says, people are often too silly to know what they want, and the result is an Horary that gives vague or conflicting information.
I suspect the real Question, that is what you
really want to know is how much of a role this man will play in the child's life. The reason you want to know is because that will dictate how much contact this man has with your girlfriend and we all know that some people are insecure and can't handle another man (or woman) hanging around the object of their affection.
In that case, the child would be the 7th House (since you don't have permission) and the father (your girlfriend's ex) would be the child's 4th House (the Chart's 10th House) and here is where the Lot of the Father would come in handy.
The Dispositor for the Lot of the Father and its position and condition in the Chart, as well as the location of the Lot and its condition should give you an accurate answer.
For example if the Lot is located in the child's 12th House (the Chart's 6th House) then that is the House of Separation and the child would have almost no contact with the father, or perhaps some contact in the first year or two or three and then none later on. A square or opposition from Mars or Saturn would indicate even less contact, probably none at all.
The Lot in the child's 1st/2nd House would indicate a lot of physical contact. In the 3rd House, the father is in the neighborhood and maybe calls the child on birthdays and holidays. In the 8th House the father provides financial support but might have only limited contact. In the 7th House, the child will probably hate the father.
The Lot in a House Cadent to the child would indicate distance, probably absence.
Of course you'd also want to look at aspects between the Lot's Dispositor and the child's significator. Separating aspects are self-explanatory, applying aspects might indicate some involvement in the child's life to some extent or another.
The child's mother would be the Chart's 4th House. Aspects between the 4th House Ruler and the 10th House Ruler (if any) will show you how that goes. Separating aspects are self-explanatory, applying aspects will show the level and nature of the contact.
