How much should I charge to babysit?

So, you're actually babysitting 2 hours, have 2 hours gap in between and then
babysit another 2 hours? Your own driving time is not relevant here, but
I can tell you that my daughter (15) gets $10/hour babysitting.

Why wouldn't my commute be considered? I would be spending almost ten dollars a day to get to her house. Thanks for the number though. I was thinking $7 but everyone is saying it's not enough. And yes, two hours, two hour gap, plus two more hours.

Your commute does not matter anywhere you work, JD3P.
Usually employers don't care if you live around the corner or have a 2 hour
drive, it's your problem how to get there, not theirs. Yes, $ 7/hour is not
enough. Your brother's girlfriend should really pay you $ 50/day which is
$ 40 for babysitting and $ 10 for in between - and only because she's your
brother's girlfriend, otherwise you should charge more.