I'm not a man, but I can imagine what most of them would say, hot sex every night.
However, since I'm NOT a man, I can tell you to cut yourself some slack. While your husband may be feeling a little bit neglected, it's only normal that you would be less amorous after taking care of twins every day.
If you can't afford a babysitter, why not make the time that they're napping special. You don't have to make everything about sex, though. Just spend time close to him, tell him how much you appreciate his providing for you and the twins, let him know how much you think he's doing a great job as a dad and husband. Make sure that he knows that as the children get older, you will be able to concentrate more on your relationship, but right now they need you. Just don't shut him down completely. Also, if he would help you take care of the kids and get them down earlier in the evening, it would give you extra time to concentrate just on HIM.
Hope that helps!