OP--Some clarifications here: He has a long history of not thinking for himself. It isn't really his fault because his parents have done all the thinking for him and continue to do so. I saw him about a year ago and nothing had changed. I try very hard to treat him as an adult when I'm around him to give him some practice but he can get himself into some bad predicaments on his own. Toots, you're right about my brother not setting a good example. When I last visited their house, nephew's bathroom (now the guest bath) had a broken shower nozzle and the toilet was no longer firmly attached to the floor. I fixed the shower while I was there and suggested they get a plumber to reset the toilet. They had just had to have their master bath repaired, at great cost, because they had continued to shower in a shower with cracked tiles until the rotted wall caved in behind it. Don't know what cause this or if there was no indication of a problem but the skylight in the master bathroom also flew off during a rainstorm surprising my brother who was sitting right underneath it!
The bathroom flood at my parent's was 3 years ago but was pretty bad and he didn't even try to clean it up--just left it.
My brother announced that he would be staying at our house without them, it was not my idea but I didn't see how I could say no since we have a guestroom. He'll be here 5 days.
We have two bathrooms, one with a tub (mine) and one with a shower. We use the shower daily and I use the tub rarely. With just a modicum of care, you can keep the shower curtain in the shower but it does require actually checking to see if any part of it is sticking out. I thought about putting Velcro in this morning and will do so.
Again, my concern is water leaking down into the empty apartment below. It is actually a 150 year old building with 6 condo units and probably isn't as water tight on the bathroom floors as a new building. I'm new to living in a condo and may be over paranoid about damaging someone else's property.
Thanks for all your ideas and advice. Hopefully, I'm worrying about nothing and he will be the perfect house guest.