The game will not allow incestuous relationships.
You will also obtain better weapons over time. It's not worth keeping as you do the same or more damage with the fist. Some can train up SPECIAL stats and others can search the Wasteland. Having a few more Dwellers than can be working for resources at a time can be helpful.It is worth your time to wait at a certain population level and increase Dwellers SPECIAL stats to increase the efficiency of your resource gathering rooms. Don't increase your population too fast.They don't need to hang out in the Living Quarters. Be sure to put pregnant women and their mate back to work in a room once they are done consumating.Give those weapons to other Dwellers that can use them. They will always flee when danger is present, so giving them weapons is pointless. Don't arm pregnant women with any weapons.Here are some tips to help you keep your Vault thriving and productive in the later parts of the game. As you go deeper into the ground building more rooms and thriving, your Vault will be more costly and time consuming to maintain. Things will get tougher as you continue to maintain your Vault by producing resources, gaining new Dwellers, and expanding the area of your Vault.