Cat wee issues - blocked pipes keeps happening despite special diet - ideas?

[HonorMatopoeia]

one of our ginger toms has had pipe blockage issues for years. He's in in vets again (thank god we got pet plan when we did!). I'm more concerned this time though as we really didn't see this one coming and usually we can pick up small signs such as excess time spent in the cat litter box and lots of licking. Last night he squatted in a corner of the kitchen and tried to wee there and that was the first we knew of it.
The vet went through the usual things including could anyone else be feeding him. Now, he's a house cat so we know he's not getting fed anywhere else but the vet seemed to think that our Dd1 (3) could be feeding him . I think this is quite unlikely to be honest as he's usually asleep upstairs avoiding her when she's awake!
So, why else would this keep reoccurring? I feel really bad because he's apparently in a bad way but we just didn't see it coming this time . Has anyone else had a cat with this problem? What happens in the long run?

All these blockage, custitis issues, usually seen particularly in desexed male cats, are caused by combination of dry feed pellets & not enough water consumption. Even when clean water provided. Cats don't drink the fluid quantities needed. Then internal heat attracts inflammation & germs. Inflammation swell urethra urine passage & blocks it. A real vet emergency as cat cannot pee or strains to. A real vet emergency. Better to guard against with a meaty water drink with some amount of squashed canned cat food eg. If cat accepting you add a bit of water to pellets, excellent. Some cats don't like any added water with pellets they love. Or watery Pet milk. Keep a watch on their hydration necessities, have no problem.