Am I calculating probability correctly? Probability was never included in my high school classes, so I'm trying to learn it now from the internet. The downside of this is that you don't get anyone grading your work and catching flaws. This is something I'm really uncertain about, so if someone could just point out my mistake or verify that I've understood it, I'd be appreciative.
Just for fun, the topic I chose to practice with was working out the chance that any of the children on 19 Kids and Counting (a TV series about a very conservative family raising children with strict traditional roles) would be LGBT. The probability of being gay is roughly $3\%$ ($0.03$) and the probability of being bisexual is roughly $4\%$ ($0.04$).
So combined, this makes $7\%$ ($0.07$). The probability of being heterosexual is $93\%$ ($0.93$). Would I be correct in saying that the probability of at least one being gay or bisexual would be $1-A^{B}$, where $A$ is the probability of being born heterosexual ($0.93$) and $B$ is the number of family members ($25$) -- or $83.7\%$?

As a followup question: there's a controversial finding by some studies, the fraternal birth order effect, that suggests that for each older brother a man has, the probability that he is gay rises by ~$38\%$, hypothesised to be due to hormonal influences during fetal development. There are $10$ boys in the family. How would I include this detail when calculating the probability? 
 A: If you assume that the event of any child being heterosexual is independent of the event of any other child being heterosexual, then the probability of all of them being heterosexual is $A^{B}$, and the probability of at least one of them being LGBT (i.e. not all of them are heterosexual) is $1-A^{B}$.  
Let's assume for the sake of argument that your study is correct. This information tells us that whether or not a child is LGBT is not independent of all other children - it depends on how many of the children born before it were male. It's not clear whether your study suggests if have older brothers increases your chances of being born bisexual. Assuming that it only affects the likelihood of being born homosexual, then the probability of being born LGBT is approximately $0.04+0.03*1.38^{n}$ where $n$ is the number of older brothers you have. This runs into problems when $1.38^{n}$ is large - your study would not be applicable for $n$ much larger than $3$ or so, due to small samples. In any case, your calculation is the same, provided you have the information of what order the children were born in.
