WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, fiance (etc.) as a dependent on your 2018 taxes as long as they meet the following requirements:
Qualifying child
• They are related to you.
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They are under the age of 19 (or 24 for full-time students).
◦ No age limit for permanently and totally disabled children.
• They live with you for more than half the year (exceptions apply).
Qualifying relative
• They don't have to be related to you (despite the name).
• They aren't claimed as a dependent by someone else.
• They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
• They aren’t filing a joint return with their spouse.
• They lived with you the entire year.
• They made less than $4,150 in 2018 (For 2019 it will probably be $4200)
• You provided more than half of their financial support. More info
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them.
As for the other part of your question regarding how much to withhold from your pay, we cannot answer that--we know nothing whatsoever about the other myriad factors that go into your tax situation.
But try the IRS withholding calculator:https://www.irs.gov/individuals/tax-withholding-estimator
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**