Advice on how to hold my cat down to cut his claws?

I hold my cats in my lap by putting their little rears in my lap so they are sitting up. I then wrap my arm around their chest and get hold of a paw with the same arm.. This helps to keep them upright. I can't say that they like it or don't try to squirm, but I usually get the job done. Since you have someone to help you, you can also have your brother put his hand under their chin and talk to them. It also helps for him to gently hold their chest up while you're doing the back feet. It's hard to explain, but I've been doing this for years. Hope this makes enough sense for you to figure out what I'm saying! I'm glad you are aware of how far to clip, avoiding the quick. Better to cut longer than risk them bleeding. The less they feel held down or trapped the better. Good luck!