Is being gay/lesbian normal/natural?

Now I don't mean to sound ignorant or mean or offend anyone. And before people get all judgemental and start rwporting me just know my bestfriend is a lesbian whom I openly support and encourage to live her life her way. It's just that I wonder, isn't it against nature to have feelings for the same sex? Shouldn't opposites attract? Isn't that supposed to be the basic design of nature?

P.S: Please channel your efforts into healthy debates and discussion rather than irrational abuses and hate.