I think you're getting your wording wrong. Dysfunctional means not operating properly or deviating from the norms of social behavior. What is defining social behavior when two males or two females have a child? Is it the aspect that it is a homosexual relationship and not heterosexual? Is that what defines the social behavior that is abnormal? One could also say that they are perfectly normal, it is socially normal to want to pursue a family, so in a since, they are normal. Remember, language is Arbitrary, it is perceived only how someone defines it, and no matter what, it constantly changes.
I also have to dispute your definition on Dysfunctional family. A dysfunctional family is a family in which conflict, misbehavior, and often abuse on the part of individual members occur continually...etc. This definition has no bearing on abnormalities with the people themselves, but more with the behavior and dynamic of the family. A heterosexual family with an abusive father, suicidal teen-aged daughter and a pill popping mother is not "normal" because they are heterosexual, they are dysfunctional because of the dynamic each individual plays on the family that doesn't follow a social norm of what a family should be like.