flexibility is a little genetic, but mainly takes a s#$tload of hardwork.
Keep stretching your body and over time it will happen: it's the Pantene promise, it won't happen overnight, but it will happen.
Also ensure you're doing your splits training on super warm muscles.
Ease them into each stretch, kind of like a heads up, I'm going to do this to you.
Then hold your stretch at the beginnings of discomfort, until that discomfort goes away.
then contract those muscles for 30 seconds, and take the stretch just that bit further.
For side splits, we recommend having your feet in a v / straddle position on the floor while watching TV, at each ad break, bend your big toe towards the floor, hold it there. then push your hips forward when the show resumes.
If you feel "bad Pain", and you'll know the difference, then take the stretch back a notch.
We've been running splits classes with a very experienced and qualified PT at my studio since July and they've made a difference.
the other thing to remember that to do the splits you need a stretch, a contracting muscles and one remaining static. ergo core is the static hold as that's holding up your upper body, and in the front splits, one leg has a contracting quad and stretching Hammie, while in the other leg, it's reversed.
Hope that helps.
xx
Miss Taken (aka Rouge)