Any tax experts?

When filling out a W4 to determine how much money will be taken from your check, do you have to claim the same as you will on your taxes?

Example: My brother is married and has a son. But on his W4 he claims single, 0 dependents. So that he has more taken out per check so he doesn’t have to pay the government as much at the end of the year. I’m not sure what his wife does on hers though.

My husband and I were talking about him doing this. But would that mess things up when we have children and I’m not working if we haven’t claimed any dependents but in facts have them?

We’re not trying to commit tax fraud or anything, just figuring out if we can bring home a certain amount while also not owing the government a ton after doing our taxes.

We live in Texas in the US, by the way.