I started out in life primarily focused on women, both sexually and romantically. I used to crush like hell on girls in my teens, and I found myself fantasizing about women. But, when it came to sexual imagery- male full-frontal nudity, etc- I found myself masturbating to both. Both sexes aroused me. But, I never even considered a relationship with a man, mainly because I just liked the women around me so much. (And I was in the theatre at the time and was young and attractive, and I could’ve had my pick of either sex. I just gravitated to the girls.)
I think that I came to terms with the fact that the relationships I had with the men around me as a child- my father, grandfather, uncles, brother- deeply skewed my mental connection with other men and delayed me finding my sexual identity because of their deep hatred and intolerance of anything they didn’t consider “manly”. That said, the few times that I did have the chance to explore my sexuality deeper as a young man in college were left alone, even though the curiosity and attraction- both emotional and physical- were there. But, this damage created by my family also transferred to my ability to form friendships with men, too, and I didn’t have any real guy friends until my 30′s.
So, that said, I think it’s entirely possible for you to have guy relationships before you have girl relationships. I think it has a lot to do with you’ve been conditioned to and the circumstances of your life. You spent your formidable years around other males, thus you’re more comfortable with other males.