Well the problem is, if you tell an Fe "I dont know what to tell you about", he can understand that as "I dont want to talk to you right now" and will respect your feelings. By the same time tho you do increase his curiosity to find out what you are so secretive about, especially when you are a relative. So best things to do with Fe people is always to feed them something, doesnt need to be something serious, just a bit from your life, like maybe a funny story you had in the supermarket or an intresting discussion you had on the internet. Dominant Fe have an unique quality, you can basically talk to them for hours about anything and tho they understand only half of it, they are comforted by the pure fact that you are talking with them and are communicating.
If you dont want to talk to them at the moment or maybe forever, you are of course in a diffcult position. Not talking anymore with relatives is near to impossible and if you do it, it will always result in them worrieing or being even pissed at you. Its like the saying "You can choose a friend, but you cant choose family".
Here's one attempt to motivate you: maybe talking more to your mother and getting on a new level of relation with her as a grown-up can present you with different perspectives and new insights about her. She prolly has some more life experience than you have and its always good to know a lot of peoples life experience, especially when you are writting stuff or when you want to develop your own self.
One critical notion: fathers generally are ultimatively calm and dont burden their sons. This doesnt mean tho that he doesnt want to talk to you as much as your mother does. Sometimes, and I know that from my own Dad, the things fathers say and the things fathers want are in absolute opposition.