Joelsnan I Googled Chevon Brown, but didn't find any details about him being in local authority care (not that I understand the relevance) nor that it wasn't about a simple driving offence. If you have any further authoritative details, I'd be grateful if you could post them.
As for his father knowing that his son would need to know that his children would need to apply for rights, I'm not totally convinced. Firstly, some people really don't know their way around the system. Secondly, it really can cost thousands of pounds for some people to be granted citizenship, which is money some people don't have. I would imagine some people just shrug their shoulders and think they didn't need to go through all their hoops and don't understand why others do. (Let's face it - we see that kind of attitude on GN all the time.) Thirdly, if he really was in local authority care, shouldn't the local authority have ensured that he applied for whatever he was eligible?
I'm not a rabid Corbynista nor do I think that the UK should be a save haven for all the world's criminals, but I do think there's something not quite right. Unfortunately, facts seem a bit thin on the ground, which is why I'd be grateful for any, if you have them.