Having two rest calls in typeahead remote.

I am making the rest call from typeahead using remote, filter functionality of it. I am getting the result of first rest call. Problem is I want to send the result of this rest call to other rest call which in turn provides the result and that results have to appended in typeahead result suggestions.
Method I am implementing is that as soon as i get result from first rest call using remote server of typeahead, I am calling the ajax function but being the asynced functionality of Ajax, typehaed is returning null results. How can i implement two rest calls in the same typehead servers.
I want the result from second rest call to be appended in tpeahead results and second is dependent on first rest call.