I want to ask a popular question. Why do many astrologers associate father with ninth house and not the tenth as you have advocated?
Many effects can come from houses that are not directly associated with the topic. For example the 7th and 8th houses can affect children, although the 5th is the house of children. Because the 7th and 8th have to do with things that have to do with children, they can indirectly have the same effect as the 5th house.
Similarly the 9th house is not defined in Brihat Parashara Hora Shastra as the house of the father, the 10th is. But in describing the effects of the 9th house, the same book very often gives effects related to the father. The 9th is the house of morals, our ability to dedicate our duties to the benefit and welfare of others. This is very related to what a father actually does. The father does this for the family, and by witnessing this, the child obtains a role model around which his morality forms. So although the 9th house is not directly the father, it is indirectly quite involved with paternal role models and the effects a father has upon a child.
– Vic DiCara