I am on H1B and green card process is on.My I-140 has been approved.My priority date is around late 2008. My family(H4-wife and children) plans to go back to my home country due to some family problems back home for at least 1 year.They have resided in U.S for more than 3 years.
1)Will this affect their eligibility vis a vis Green card process?
2)If they have resided in the U.S from Jan. to May 31 2010,can they be claimed as dependents and can we file joint returns at the end of the financial year?

My employer is filing for the green card on my behalf.
Please advice me,
Thank you

Yes, you will be able to file jointly and claim your children as dependents for 2010.

As long as the return to home country is only temporary, it probably will have no effect on your green card submission, but I am NOT an immigration attorney, so I am not sure about this.

Best you post this question in the LAW forum under Immigration Law to be sure to get one of those expert's opinion on the matter.