Alright, well that's good. That's how many reps you should be doing. I guess in that case, i'd bump down the weight slightly on the exercises that you're doing 8 reps on. Bump it down slightly for those and do like 9 or 10 reps instead of 8. I think that should help. It doesn't sound like the reps are the problem to me, it sounds like the weight is a little too heavy.
Anyway, hope this helped man. It sucks to be so sore you don't wanna workout the next time.
Edit: Also, i just saw that you said you just started working out again with your brother. I'm always pretty sore the first week after taking a long break, but stick with it. After you get a couple weeks under your belt it gets easier and easier.