My sis is still on ML and spends her days doing what she wants and ignoring everything else
With a 3 year old and a 6 month old baby, I very much doubt this statement. Are the children properly fed. bathed, and kept in clean clothing? If so, then that's not true at all. Just keeping up to speed with that is an all-consuming and relentless daily responsibility.
Fuck the state of the house - biscuits ground into the sofa, dried up beans under the kitchen table, grimy handprints on the wall - that's all normal (ish). When you have toddlers you have to lower your hygiene standards. And that's a fact. I used to be up your arse houseproud,
until I had two children, and my firstborn with a SN syndrome .My second born (who has no SN) is still appalled at the mess her sister can make
in five minutes flat. So in my opinion, a messy untidy house is not a case for SS.
I don't think it's at all out of order for a 14 year old to change a baby's nappy to help out. And I don't think it's unusual for a 14 year old to comfort a toddler whilst Mum is otherwise engaged with a baby. It's what families do. On the other hand, it's quite possible that this 14 year old is being put upon beyond what is normal - but only the OP knows
which one of those scenarios is nearest the truth.
I'm quite prepared to be shot down, but I suspect OP has no children, and what I would suggest is that she rolls up her sleeves and offers a bit of hands on assistance. Because that's what families do as well.
If I'm wrong, and she has a genuine worry, and if the baby is 6 months old then OP has recourse to contact a Health Visitor. SS can be a real help in many desperate situations, but I think it should be only in the most worrying situations that they get involved. Their resources are severely limited, and we don't want to call them in to look at a messy house and a Mum temporarily overwhelmed by childcare when their time might be needed elsewhere by children who are receiving genuine abuse.
Only OP knows how bad this situation is.
Are the children abused? Or is Mum just isolated and overwhelmed with looking after a toddler and a baby without any help from anywhere?
Is it all just getting on top of her?
Be helpful and not judgemental. And keep talking to the 14 year old 