The link given by another member will give you more info.Some thing I would like to share are based on my recent experience.
The main consideration during interview is , you have to demonstrate strong ties back home to convince the consular officer that you will return after the visit.
having blood relations in US is always a challenge and goes delta.
It depend how long you are in Doha or any other countries.Bottom line is you have to prove that you will leave US after the proposed visit.
I got 5 years visa and some of my friends got an year or less. It all depends on the consular officer taking interview.
They normally do fair with all, if your case is genuine you have a chance. provide all documents to demonstrate you will not stay back in US. all the best !!