Actually no.
"is the affectional or loving attraction to another person. It can be considered as ranging along a continuum from same-sex attraction only at one end of the continuum to opposite-sex attraction only at the other end."
www.bouldercounty.org/health/commhlth/safezone/LGBTIQ/definitions.htm"How one thinks of oneself in terms of to whom one is sexually and/or romantically attracted. Orientation is dependent NOT upon physical experience, but rather on a person's feelings and attractions."
members.tripod.com/lavendar_women-ivil/id13.html
As you can see, no definitions make reference to natural belief.