Welcome to the wonderful world of lighting. I'm assuming that you are using flash, rather than continuous lighting, so read my comments in that light (ahem).
From your comment, I gather that you intended to use one light as key, and the other as fill. The strength of the light on the subject is affected by a number of factors, including the output of the flash (both GN of the unit and relative power actually used), type of modifier and distance from the subject. It may be that one of those factors caused you to get a different outcome than you were expecting. Experimenting will quickly give you a good idea of how to achieve the key/fill effect that you are after.
I find that, for single subjects relatively close up (like this), a single light with large modifier (e.g. umbrella) close to the subject often gives you enough wrap around light that you don't need a separate fill light - which can make things more portable and quicker to set up.
Generally, using flash lets you take more control over aperture and ISO than shooting with available light. For example, your flashes should give you enough power to be able to take this photo at, say, f8 (for more DOF) and ISO 400 or below (for better noise control). IME, those settings are a sweet spot for simple and effective single person portraits using flash.