For front splits: Very deep lunges to stretch hip flexors, hamstring stretches, then get as close as you can, preferably supporting your crotch (‘sit’ on a small stool, then a yoga block, whatever supports you in the position) so that you can relax into the pose.

Best to do these after a workout while you are warm, then again before bed when you are cool, and go to your edge but not past it, that edge will move.

For straddle split, I don’t know if everyone can get those but my nearly 60 year old husband can, and mostly he just lifts weights, so maybe. Those you can practice hot or cold, and if you do the widest you can and lean forward for 5 minutes it will also relax you for sleep. So good practice for bedtime.