Nanny share and taxes

[Anonymous]

I would love to hear from nannies who do/did work in shares how they ended up with taxes. This is my first year working in a share and thats what i heard... I am paid $1100 a week, $570 one family and $530 the other one. We found out that i might be owing money next year because i will be in a different tax bracket. Right now it looks like my income will be around $30000 (is based on single income which is $570 * 52 weeks) but when i fill out my taxes my income will double and i will fall into a different tax bracket. Im married with one child and already put 0 allowances on my W4 form.
Im a little bit confused and thinking that making more money in share makes me pay more taxes.