Can someone be both narcissistic and borderline?

Ive always believed that my husband is borderline. He was diagnosed once, during one of our crisis, but I have a feeling his psychiatrist also mentioned narcissistic personality disorder because he has given hints in the past.

That crisis passed but we had many others and he stopped getting help.

I'm wondering now if he is also a narcissist because he doesn't have much empathy at all, and everything is centered around him. However, he has very low self esteem, and doesn't think highly of himself at all, so that's confusing.

Example of how his mind works: it's 10pm and I'm exhausted. I want to sleep. I asked him to turn off the lights and remind him he also needs sleep (he complained about it a few hours earlier). He starts fighting that this is his only time to relax and be on his computer. I say I understand and asked him if he could please do it someplace else, before deciding to come to bed. He then gets angrier and starts retelling the horrible day he had and that this is his only time to unwind. I try explaining to him that this is not about him relaxing or not. It's about how this is affecting my sleep and that there are other places he can go surf the net.

Anyway, he doesn't understand my point. He goes back to making this about him, about his relaxing time when we both should be sleeping. Basically making it out to be that I'm being unreasonable for wanting to sleep when he wanted to keep the lights on to do his relaxing. Is this narcissistic?

Well there is a long answer and a short one. The long one has to do with the differences between egoism and narcissism and with the different ways that narcissism and borderlien can be looked at in psychological theory, which can make a comorbidity either possible or impossible depending on the position you have taken.
The short one is, why is it relevant? I would say his actions are egoistical or in a way I would call them autistic, in the sense of that he realizes only his own needs (/existence) while blocking out yours, while being in these states. It can be a side-effect of his BPD, or of something else, just like lack of empathy that can be caused by BPD but also other illnesses.
Question is just what difference does it make in terms of what can be done about it. Both disorders, if you want to get rid of them, take a lot of time [and money] and require the patients own will to go thru it.

I am co-morbid between both (clinically diagnosed by a psychiatrist), so yes, it can exist. Usually one is stronger than the other. My NPD significantly outweighs my BPD. When dating, I am more fearful of the lack of validation versus being abandoned.