Can I bring my sister to united states even if she is married?

You can petition for your sister and her family but those types of petitions take about 10-12 years so she will not be able to come to the US as an immigrant for quite some time on the basis of your petition.

*Family Petition* A family petition must be prepared based upon the relationship of the petitioner and the beneficiary. These petitions do take some time in order for the visa number to become current. However, if you do not start the petition now, then the priority date will not be set and the wait will simply be longer.

The answer to your question is yes. A US citizen (USC) can submit a Form I-130, Petition for Alien Relative, on behalf of her sibling to accord that foreign national sibling an immigrant visa as the brother/sister of a USC. Unfortunately, the waiting period for a visa to become available in this category is upwards of 12 years. This means that once you file the application, a "priority date" will be assigned and this will mark a place in line. There are yearly limitations on the availability of visas in this category and you can understand, ther are many more individuals who apply for these visas than there are visas available. So I would suggest that you submit the Form I-130 and obtain a spot in line. This is not the most difficult work to handle, but it may be worth it to hire a lawyer if you are worried about doint it right. At the end of the day it isn't that difficult to do and can easily be done by someone without th need of a lawyer. Once the visa becomes available, I would highly suggest hiring a lawyer, but as indicated above, that will certainly take quite a while. If you do decide to hire someone. Speak with someone who is licensed and someone who knows what they are talking about with authority when you speak to the lawyer. There are a lot of people out there that will gladly take your money and run. Find someone who is reputable, there are lawyers out there who are honest and will do right by you. Good luck.

Assuming you are a US Citizen, you are allowed to petition for your sister based upon the family-based F-4 classification even if she is married (her husband and minor children would potentially be derivative beneficiaries of her petition). The problem you face, however, is that once you have filed the initial I-130 petition on her behalf, there is a long multi-year backlog in availability of immigrant visas in that classification. In your case, visas are now being processed for individuals from El Salvador who have established priority dates (from the prior approval of an I-130 petition) that reflect a date of 01 December 2000 or older (based upon the May 2012 USDOS Visa Bulletin tables). This means that those individuals who have already gone through the I-130 process are waiting for immigrant visa availability for their siblings under the current system for a minimum of 12 more years (or longer), unless the US Congress were to change the quota system and increase such visa availability.

Yes you are able to file a visa petition for her.

Yes. You may petition for your married sister and her family on Form I-130. Her husband and unmarried children under 21 years of age may immigrate with her. However, the wait period is about 10 years before she can immigrate.