Just to clarify, the aforementioned disproportionate representation is with "street children" not homeless youth as a whole.
b) From the literature I looked at, and the very wikipedia article I linked, it is true for homeless youth as a whole.
E.g. the very first sentence in the abstract:
> A disproportionate number of lesbian, gay, bisexual and transgender (LGBT) youth experience homelessness each year in the United States.
in