There is no sexual activity in CoE. If you make a childcontract with someone of the other gender, a child magically appears. You cannot do this every hour, there is a cooldown of (not sure but I think) 1 year, so 1 rl week and the cooldown does not depend on your gender. Pregnancy is not a thing either. The childcontract says, whos child it is and the person that gets the rights can chose those bars between the stats of the parents. A heir doesnt have to be directly related, you can decide whos your heir quite freely. Still, the easiest way will be getting some children with different age and making that one your heir that you intend to play in your next life. Taking heirs out of the world to prevent them being killed is outdated.