What increases the chances of having sons in Rome Total War? I need them for heavy generals ( I have 76 daughters and 3 living sons). Is there a "Special" trait that would allow me to have more sons and to continue my family chain?
Of the available Traits that affect fertility, there are none that are gender specific.
Given that you have so many daughters, you should be getting offers from prospective husbands. That is assuming that your daughters are of age and not already married (or widowed).
The only reason for having more probability of sons is getting more territories, even if one of your general is Infertile can still have sons.
Fertility trait is believed to increase probability of having children, but only affects the chance of the new child belonging among the living generals of your family.
I have tested many configs on Rome TW, and those are my impressions about this topic. Try also to not lose your generals too often.