Even though these two questions may not be answered in the Bible to our satisfaction we do know some things for sure. Homosexuality is here. People (heterosexual and homosexual) engage in sex other than just for procreation, or my parents who have two children would only have engaged in sex twice their whole lives.

The Roman Catholic church has been one of the staunchest supporters of the notion that sex is ONLY for procreation purposes and has of course condemned the use of birth control measures. An interesting article published in 1975 shows that the Vatican does not hold that view in all contexts. The paper "Declaration on Certain Question Concerning Sexual Ethics" released from the Vatican states that "for some individuals homosexuality is an innate instinct."  The church in Rome admits that for some people homosexuality is who they are as created by God and of course homosexuals cannot procreate, so these sexual acts (although discouraged by the church) are accepted by the church as innate even though their intent is not procreation.

Hence we have answered the first question - sex is not solely for procreation. We have also hinted to an answer for the second question.

Homosexuality came into being some time after the original creation - many things did: races, languages, countries, etc. History (secular and religious) is silent as to the origin of homosexuality, but it is clear that it dates back to early times. Also, homosexuality is not confined to humans, as it has been noted that many (if not all) species engage in such behavior.

A point of clarification needs to be made - the Bible is not a textbook on sex, nor should it be. The primary purpose of the Bible is the revelation of God's plan for eternal salvation - everything else if it is not directly relevant to that end is secondary and at times ignored within its pages.

With that said let's re-visit the second question. How many of you or people you know are left-handed? A minority - it is a biological variation, being right-handed is the "norm" and many lefties find that functioning in a right-handed world can be difficult. The early church actually shunned such people and attempted to force everyone to use their right hand as using one's left was considered to be against God's will and the work of Satan.

How about having red hair - do you know someone with that hair color? At one time that biological trait was considered a mark of Satan. Take skin color - many religions have throughout history taught that black skin was a curse of sinful behavior and to be despised. The list goes on and on.

Deoxyribonucleic acid (DNA) is undoubtedly the most complex chemical known to man. Subtle changes within this genetic material can have "profound" effects on offspring; from hair, eye, skin color, height, weight, gender, sexual orientation, susceptibility to disease, mental capacity, etc... and yet with all those "profound" differences we are still people - so maybe those differences are not that profound at all.

To give one example of how complicated sexual identity is, let us look at the chicken.  Periodically a male chicken, rooster, will be compelled to act like a hen (female chicken). He will try and "steal" a hen's eggs so that he can care for them. Since most hen's are protective of their eggs the rooster normally has to settle for nursing small rocks.  In this case the rooster has clearly taken on the identity (at least in his mind) that he is a hen.  A more astounding and definitive example is that of hens (female chickens).  Hens have two sexual organs or gonads (like humans, where men have two testicles and women have two ovaries). The chicken's right gonad is differentiated, meaning that it specifically has developed into an ovary and this is what the hen uses in sexual reproduction.  Interestingly, the left gonad is non-differentiated and is not used unless the right gonad becomes damaged.  If the right gonad becomes damaged, the left organ will change into either an ovary or a testes. Meaning that the hen may remain a hen or it will become a fully functioning male chicken, or rooster.  These examples show that even  physiologically sexual identity is vague.

To complicate matters, the definition of one's sexual identity is based on four components: genetic (chromosomal), anatomic (physiologic), psychological (mental), and sociologic (cultural). Genetic refers to the chromosomal makeup of a person (how one is built on the inside). Anatomic is what does the person look like on the outside. Psychological refers to how one visualizes him/herself. Sociologic refers to how society refers to or visualizes that person.

From a genetic point of view there are a number (approx. 0.1% or 6,000,000) who are classified as inter-sex. Chromosomally (i.e. the types and quantities of hormones produced) their bodies behave like one gender and yet their exterior or anatomical aspect resembles the opposite gender. There are also true hermaphroditic humans. Scientifically, they are defined as having some functioning testicular tissue (male reproductive tissue) and some functioning ovarian tissue (female reproductive tissue). Relating this back to the ignorant statement "God didn't create Adam and Steve", exactly how should an inter-sex or hermaphroditic individual be classified: Adam, Eve, or Steve? And should it be suggested that he or she was not created by God. Once we recognize the complexity of determining one's sexual identity, we become aware of the massive amount of diversity created by God.

We have the tendency to see differences much easier than similarities and tend to shun, fear, despise those differences instead of glorifying God's creative diversity. So that we don't feel like we are arbitrarily discriminating we tend to incorporate our dislikes into our religion and claim that we don't judge or dislike these differences, but rather God does and we are just following His example.

God created us. He created DNA. He knew the diversity it would create and in the first chapter of Genesis he stated "It is good." So yes, God created Adam and Steve. And it is good.

When the disciples asked Christ why God created people who are blind and was it because that person or his parents had sinned. John 9:3 "It is not that this man sinned, or his parents, but that the works of God might be made manifest in him." God has created each of us so that the works of His can be made manifest in us. GLBT people are not accidents, errors, perverts, but rather chances for the works of God to be manifest. 

References

Helminiak, Daniel A (2000) What the Bible Really Says about Homosexuality. Alamo Square Press