Birth citizenship ?

Yes. A child born in the USA is a USC.

Will my parents with green cards be able to enter US after being away for more than 6 months?

I agree with my colleague. The requirements for maintaining LPR status are clearly explained and it is the LPR's responsibility to know those...

Will I qualify for E2 visa ?

None of the information you have provided is relevant to whether you qualify for an E2 visa. Consult with an experienced immigration attorney to go...

The visa is not transferable. You apply for an H4 visa on behalf of the child and I suggest you do so.

The maintenance of an H visa is the same for Canadians as for all others.

Citizenship?

Whether you are eligible for NATZ depends on many factors. To determine whether you qualify read the publication; A Guide to Naturalization, found...

Can a US citizen get in trouble for this with immigration ?

Yes. USC's can be charged with marriage fraud and if convicted sentenced to prison and or fined.

If my us citizen wife is not working but she want to sponsor me to get my green card,can she use his brother as a joint sponsor?

yes. The brother would be a co sponsor. She must be the primary sponsor regardless of her income.

Question regarding Humanitarian Parole for foreigner is already in US?

Depends on the terms of the parole. I suggest she consult with an experienced immigration attorney.

Which forms I must apply ? or if there is any why I get a one year visa until the green card process finished ?

I strongly suggest you consult with an experienced immigration attorney. Your children may be USC's and it is a matter of technicalities to get...