My son struggled massively with night time bedwetting. At 15 he is now mostly dry and a wet bed is very rare. He is autistic.
I bed wet until around age 13 due to neurodevelopment disorder.
It is highly unlikely to be “shit parenting”. As a HV I have seen truly neglectful parenting. Funnily enough their kids tend to get dry at night rapidly perhaps because Mum and Dad won’t bother with things like changing sheets. They tend to feed themselves from what they find in ththe fridge and cupboards too.so weight often isn’t a concern either.
As many have said night time dryness is a mix of things coming together. Hormones released at night to tell the kidneys to slow down vary in when they get released and children tend to be different ages. Usually 1 in 10 kids are still bedwetting age 7 so it’s very common.
OP you’ve been left in a crappy situation.
I second all the advice about bedmats
Mattress protectors can be bought very cheaply too. In the case of the 8 year old I would see if she is able to strip a bed. If she can then put a clean sheet on, pop bed mats over the top and another clean sheet. Give her a change of clothes if needed. Then if she wakes up she can simply pull the wet stuff off, change her clothes and get back into bed on the clean sheet underneath.
More general advice.
Let them drink properly during the day but only half a cup of fluid in the two hours before bed.
Avoid hot chocolate as it stimulates urine production (from experience).
Get them to empty their bladder before bed and then again before they sleep if possible to squeeze out any last fluid.
However if the younger child is producing a massive amount of urine within two hours of falling asleep then the likelihood is that his brain is not yet telling his kidneys to slow down and that’s an age/development issue which will resolve itself as he gets older.
Wish you were my sister, I’d send the teenager straight over
. He’s a rad moody but you just need to throw food at him a few times a day to keep him amenable.