Not all Daddy Doms or Caregivers are straight. I've seen a number of male Caregivers identify as bisexual, pansexual, or homosexual. I'd say that those orientation preferences are probably less common but definitely not unheard of in the community.
I was interested in a little recently who is in a poly. relationship. He identifies as a little male, and one of his partners identifies as a homosexual Daddy Dom male. I am almost sure his definitely-not-straight Daddy Dom isn't the only homosexual dominant interested in Caregiver/little dynamics.
It's kind of the same as vanilla life. Most people seem to identify as heterosexual, but definitely not all people.
Remember that your relationship status does not define who you are though. Finding a non-straight Daddy Dom person may be less important right now than you think, and, oftentimes, people reflect on their past and feel that their wait for their knight in shining armor was well worth it.