two headphone hookup

other than having a microphone splitter, is it possible to have two headphones hooked up somehow? from what i hear, the splitter degrades quality.

i was hoping to monitor in on a recording session (vocals and music) where the singer sings into the mic and has the monitor over her ears.

would i need an external sound card to retain quality for both monitors?

Your best bet is to get an audio interface or a powered digital mixer.
There are thousands to choose from depending on the connections you want and your budget.