Yes splits are possible, but it's a question of how comfortable you are whilst doing the exercises. Sumo wrestlers in Japan (and across the world) can usually do the splits, as it's predominantly the underlying muscle that needs stretched for splits.
The most useful link I ever found was here and I've used it successfully through martial arts training. The main thing to be aware of is when you're stretching for splits you're also stretching joints, ligaments, skin, tendons, etc.
I'd recommend doing splits on your knees, similar to Taekwondo practitioners, to avoid [major] joint problems later in life. Whilst not a complete deterrent to joint problems, the weight distribution will not be on your knee and ankle joints, and mostly focussed on the parts that need stretched (initially).
Some final points:
- Always warm up
- Do not push through the pain
- You will also need to strengthen and increase flexibility in your supporting muscles
- Use breathing to relax, by breathing out whilst 'applying' the stretch
On point 2: Initially your muscles need to learn to relax before the stretch (I believe this is referred to as the stretch-reflex in the link where the body tightens prior to stress/impact).
If you have any pains or problems other than a bit of stiffness in your stretched muscles, check with your doctor. People that are considered 'fit' have done more damage to themselves by ignoring what their body tells them.
