What house is Mars in? Any aspect to Mars?Mars in Aries typically likes straightforward, quick sex. Nothing long-winded or too complex.
But if in aspect to Mercury/Moon for instance. Or Moon/Mercury sharing the same house, there could be added complexities.
Gemini Mars time( barring other factors like house position, aspects etc) is more into mind sex than just physical gratification. They want to be turned on mentally and enticed there first.
Aries likes Gemini's versatility. Gemini can be the aggressor and passive one whenever appropriate. And is forever into trying new things and exploring sex.
But Gemini is a lot less passionate or "all in". As their mind is more detached and inclined to observe from a certain distant place. As air does this intrinsically.
So Aries may feel like Gemini ain't really into them at times or is " elsewhere" when they get intimate. Even when Gemini is "ohhhhhing" and "ahhhhhhing" etc.
There are certain inherent issues(barring aspect to mitigate them). As the two approaches do differ somewhat. But its not completely an incompatible pairing.
If he has Mercury in Aries/ conjunct his Mars in Aries for instance. The Mercury not only makes a mutual reception with your Mars in Gemini. But Mercury/Mars in aspect is synonymous to Mars in Gem/Virgo.
So there is plenty understanding and meeting ground. As the cerebral approach (Mercy) is also likely with him when engaging in intimacy (Mars)