How do I know if there is mold between shower lining and the wall?

The leak is my little brother taking very long showers, up to an hour or so, and constantly getting out of the shower, several times (10-15) dng that shower, without drying off, then leaving the floor wet, along with a soaked wet towel or two left on floor. He won't use a fan or open the window to vent out any moisture. The walls, mirrors, and ceiling all wet. He uses my dad's master bathroom, and now my dad is having a hard time breathing when he wakes up in the morning, hacking miserably, which is getting worse. My brother won't let me clean the bathroom,he hates the smell of bleach, but I wait for him to leave, and do a little bit at a time. I'm so worried about my dad. I talked to my brother, but he won't change his ways. My brother is disabled, he suffers from manic depression, so my dad won't correct him, he'll throw a fit.

Yes, the subfloor in front of bathtub is showing and it is soaked, so I'll replace that, first thing. I just have to figure out what I'm going to replace the flooring with. My dad just wants to caulk up the old vinyl flooring. He didn't even want me to replace the damaged subfloor. I explained to him that if he seals up the wet subfloor, it will rot. The floor around the toilet is sagging some too. I was thinking of vinyl panels. I have to do repairs while family members step out for the day (3-4 hours.) They will freak out, if they see me have anything apart. Very stressful!

Yes, I know, that's why I'm so worried for my dad to be breathing in all those mold spores. I can smell it in his bedroom now, and it's getting worse. I had cleaned the mold from that bathroom before, a year ago, that took a day or two. I was feeling sick from breathing all the bleach. This time, I am using hydrogen peroxide & baking soda. white vinegar, soap & water, and I'm going to try the tea tree oil (20 drops+1/2 cup water.) Bleach worked to remove dark areas the best, but my br

It's my brother taking hour showers. He also has a new habit of getting out of the shower several (10 +) times during his shower, dripping wet ( If he hears noises, talking,the phone, or the TV, he'll jump out of the shower dripping wet, coming to see what the noise was.) leaving the floor wet afterwards along with a couple soaked towels, he doesn't open the window for ventilation or exhaust fan. After his shower, the floor, walls,mirror, and ceiling are all wet from condensation. His showers are getting longer. The other day, the water was running for over an hour & a half. He's been developing this strange habit since our mom died. Shorter showers, dry floors, and more ventilation/open window would help. This is the second time we've had mold in this bathroom, in 1 years time. Never had mold problems before this.

I tried, he's a very difficult person. He just doesn't get it. He doesn't seem to care about any damage he causes, and he's not going to like it when the bathroom is getting fixed and he won't be able to use it. He's going to throw a fit! I have to replace the subfloor,

in tub area and at toilet, replace baseboard, maybe some or all walls, add trimming, and I think I have to rip out all of the ceiling, it looks like the mold has saturated through.

Wish me luck!

left trailand that left dark/ streaksr keft tile flooringsubfloorI'm going to make sure to Waterproof like crazy

That sounds good! He's in his 40's though, he won't listen. He's a big baby too! Maybe I should just take out the bathtub and leave it out. No, just kidding! If my dad has to call in the pros, it's going to be very costly and he won't let my brother forget! Well thank you for your advice! Have a great weekend!