My boyfriend is in the process of moving in. I had a full 6 months of EF, but had to dip into it for a car situation. My EF was based on me living alone; since he is moving in, should I base it on my share of expenses? Anyone living with a SO, how do you figure your own EF? 
Base it off how much it would cost you to live without him. Relationships aren’t guaranteed, and you don’t want to be in a situation where you feel stuck just because you can’t afford to separate.
Also, people have car accidents, lose jobs, have emergency surgery, etc., daily. You need to be sure you are covering all expenses for living in case you end up with only one job supporting.
If you’re not married, you keep everything separate. Emergency funds and budgets included.
Based on your total expenses by yourself, not only because relationships aren’t guaranteed but also one of you may get laid off or sick.
I base my EF on the cost of living alone 'cause a worst-case scenario where I might use my EF would be a breakup where I have to go back to living alone.