Yes, that is correct - but only the moveable estate: money, jewellery, cars, etc. That's been the law since the 1960s. Whether the children are 'natural', adopted or 'illegitimate' makes no difference.
If a child has died, then their heirs can claim. Moreover, they have twenty years in which to make the claim.
When my husband died, his children and grandchild actually got over half of the moveable estate. I was executor and the main beneficiary. The solicitor kept emphasising that I was giving them more than I had to. (The will was written before the grandchild was born, but DH told me what he'd like me to give her. I gave her extra.)
If the children have been left something in the will, they can choose whether to take that or their 'legal rights' - usually, whichever is the more.
Often, children decline their 'legal rights' in favour of their mother.
When my husband died, the solicitor wanted to send a form letter asking whether they wanted to claim their legal rights.
I told him no - he was to write and tell them that the cheques enclosed (and the jewellery, etc) were their legal rights. I also asked him to write to the grandchild, telling her that she was being sent a cheque as per her grandfather's verbal instruction. (I actually gave her more, but she doesn't know that.)