I had a will. (And my previous will included the possibility that my brother might have children, or that my sister might have more children, so technically my newest nibling was covered.)
But, named bequests are better, and this month is
Will Aid month, so I looked up the nearest solicitor to me who was participating and this time, helped by the fact that the solicitor was doing it for free and so had no investment in making it more complicated, I had him write me a classically simple will with a small handful of cash bequests, an explicit instruction to my executor to honour any handwritten bequests that had been dated and signed (legal in Scottish law: I don't even have to get a witness), and the main division of residual legacy* to residual heirs, this time including both nephews by name.
But, as the solicitor pointed out (as the last one did) there is the possibility that either my brother or my sister might have more children, and so there's an additional clause adding any other offspring of my brother and my sister as equal heirs with the two named nephews. When the will arrived, these potential niblings were identified as "born or in utero at the time of my death" - and this actually left me wondering - in the kind of way one does speculate about wild improbabilities - what happens if my brother's girlfriend is pregnant at the time of my death, then has a miscarriage afterwards? Would the dead fetus get a share, which would by default be inherited by my brother's girlfriend? The whole thing has a massive improbability score which I am not seriously worried about - not least, because it's not as if I'm actually going to be around to worry about it if it happens - but it's a curious thing to will money to a fetus.
Anyway. I need to get the will witnessed and a copy in store, but once done that should do me for another ten years**. Unless Flow
is planning to give newest nephew a sibling. (My sister has already, many times, said emphatically that there are not going to be any more from her.)
Anyway. Making a will is important! Even if you have nothing to leave except twelve books and three sex toys and a kitten, the only reason for not making a will is to cause guaranteed amounts of trouble for whoever is required to deal with your crap after you die.

*My house. When sold.
**Unless I buy another house in the meantime. Or register a civil partnership. Or the world as we know it comes to an end in 2012. Or have a baby. I mention these things in increasing order of wild improbability, but any one of them could invalidate*** my will.
***Not legally. In Scotland nothing invalidates a previous will but a new will, though you and your heirs and executors ought to be identified by name/address, and a spouse can claim a share. And Scottish courts can process Scots law anywhere, so technically it wouldn't matter if the UK was completely drowned by giant tsunamis. Actually having a child would make a will effectively invalid since a child is legally entitled to a specific share in a Scottish will and can contest the will if they don't get it.