When to believe and when to really question.  I think we all, as parents, want to initially believe our children when they tell us something.  We instinctively believe they are being honest and wouldn't consider not telling us the truth.  I remember the first time I viewed the television reality show " Christley Knows Best" and all that he kept saying was "Kids they always lie, never tell the truth and you can never believe them".  I think children go through an age where they truly test parents to see how much they can get away with.  When my daughter was little she would tell me something, okay, I believed her, but then I found out the truth.  She wouldn't know that I found out and I'd ask her again, "Are you sure you did this?"  She always would give me that look like "does she really know?" and I would tell her "I always find out, God meant me to find out everything, so if you think you got away with it, think again!".  My daughter is the one who looks danger in the eye and says I can defy you, and always takes the risk.  Need I tell you I ALWAYS FIND OUT!.   I mean really, I find out.  I don't know how it happens.  She got into a car accident, and tried to talk her way out of it, I just happened to be driving by the area and saw her car.  Immediately I drove in and she stood there with this dead look on her face when she saw me.  "What are you doing here?"  Did  I not tell you I always find out.  So as the time goes by, my son thinks he can play her games with me.  "Did you brush your teeth?"  He replies, "Yes I did", "Really, let me see?" Immediately I get the death look, " Did I not tell you I always find out?"  And from the next room you hear "Listen to her she's right, she always finds out".  I think God made us psychic like that, it's not that you don't want to trust them it's just that you know better.
So with two children with disabilities, they are trailing each other.  My daughter, now 18 and feels that this age makes her much different from us all.  I laugh, really what does 18 really get you?  Your not legal to drink, you can get a job, but she doesn't, she doesn't own a home or rent, she doesn't own a car, so what does 18 years old really mean????  Nothing!  But it does mean, in order for me to talk to her doctors, she has to sign a waiver, that she gets all her grades from college and not me even though I pay all the school bills!   With her ADD, she emotionally is thinking like a 16 year old in a 18 year old body.  In college this is a potential issue because common sense has not set in, really I think common sense happens as the children mature but in these children it takes more time.  She's rebelling against her drugs, this happens.  I try to tell her that in the long run these help her calm down and really focus, but it's that 18 year old kid with a 16 year old mind.  So when do you believe, well now, with two the same way, I listen, think about what they have told me and question every move.  My daughter calls this over protective, I call it Mom's instincts.  Do they still try to pull the wool over my eyes?  You bettcha!  That's why I question everything, check up on everything, have cameras in my house (don't forget the boys!!) and first give them the benefit of the doubt, until it doesn't feel right, then investigate!
Good Luck!