How long does it take to get them in US if I am a citizen?

Although a U.S. citizen may sponsor a sibling for immigration benefits, there is a very long backlog for visas in this category (the Family-based Fourth Preference ["FB4"] visa category). While the Visa Bulletin issued by the U.S. Department of State may seem to indicate a shorter backlog, it is likely that for a newly filed case no visa will be available for 15 - 20 years or longer. For this reason an FB4 application rarely is a satisfactory immigration strategy. It would be wise for your sister and her husband to consult with an immigration attorney who, after learning all of the relevant facts about them (including potential eligibility for an employment-based visa), could advise about eligibilities, options and strategies.