Set them up for success. A regular chore done on a specific day helps and an actual visual chart that they can tick or stamp (much more fun) will help too.
No cash is paid in this house for any chore. You do the chore to get what you want, the ipad, tv, a trip to the park etc. No one pays me as an adult to do a chore.
At the age they are, set the table, clear a table, put items into the dishwasher. In school they would both be made to tidy up any classroom activity that created mess. The same with their school dinners, they are responsible for taking the tray back, scraping the remains into the bin etc.
Mine also stripped their beds, they can do it together and the 11 year old can definitely put her bedding back on her bed. You can assist for a bit but ultimately she needs to do it.
You need to have a talk to them and point out that you do not live with your parents and they at some stage will not live with you. All the things you and your Dp/Dh do they will have to do too and now they have to learn those things.
Yes, standing over them is relentless but my children knew I would never back down so just got on with it although mine started younger. If they leave a mess anywhere you interrupt them playing and make them come back and clear up. I even delayed putting a load of laundry on so that they would turn their inside out socks the right way out.
Yes you will be met with complaints but you need to stop pandering to them. My children are young adults, they still live at home so you might end up with this going on for 15 years, is that what you want? No, so dig in now. Have a song, something that helps you keep calm that you sing or even play via a headphone in your ear.