He isn't two yet. He is weeing by himself approx once a day. Pulling his own trousers and nappy down and then telling me he has done one. I have no involvement and am offering no encouragement or incentive.
I have two older ones who I just left until they were ready, no accidents, they just went straight into pants and that was that. (DD was 22 months and DS1 was 2.11)
This time, I forsee much more effort and many accidents, but he is clearly ready to start proceedings.
Why does it matter if you're not ready? You say DS2 is clearly ready to start and you assume more effort and many accidents, but you don't know for sure. Are you basing this on the fact that DD trained at under 2, DS1 at 2.11, so boys are always later to train? Give it a go, if no success after a week go back to nappies.
When you say he takes his nappy off by himself and wees unaided, do you mean in potty or toilet, or just wherever he is at the time, because that makes a big difference. If in potty, he's ready, if anywhere he isn't.
Sorry but your post is rather vague and the circumstances in which you train are important. If you had mentioned for example that you are emigrating next week, the answer you get might be different.
We are going on holiday to France next week, but only to my parents, so nappy off time would be fine.
Yes, I am basing my thoughts that he is a bit young on generalisations and mine and friends experience of potty training.
I just don't want to have to 'train' him. As I said the other two were more ready and could go straight into pants. DC3 is only weeing reliably once a day on the potty, I want to wait until he is doing nearly all his wees on the potty.
He isn't weeing anywhere, he is weeing in his nappy or pulling it down and weeing on the potty.
Why not have a routine of potty times, as well as nappy off time, DS2 goes on getting up, and at intervals until bedtime. Put nappy on for sleep. After meals is a good time to try for a poo.
If you find he stays clean and dry most of the time, and can put himself on the potty in advance of weeing and pooing, I'd say he's ready. You can still do the potty routine and keep him in nappies, it takes no more time than changing the nappy anyway. He shouldn't sit for more than 2-3 minutes, unless you can tell he's about to poo.