I think it is. If you think of anarchism in terms or class struggle, opposition to the state, and the rejection of hierarchy and power relationships, then the rejection of patriarchy and the goal of non-binary gender equity is very much a part of it. Anarcho-feminist Emma Goldman was one of the first anarchists to recognize and revile societies' insistence upon rigid, binary gender roles and was an early (and solitary) proponent of the concept of fluidity of gender and support for the rights of gays and lesbians.
In terms of contemporary anarcho-feminism, sexism, transphobia and patriarchy are viewed as an inequity of power relationships used as a tool of oppression by the state and the society it engenders. As an anarchist - whether you identify as male, female, neither or both - addressing the inequity of power relationships and critique of the state as based in power inequity and class stratification, it is no great leap to see patriarchy as the most glaring example of those inequities.
Does "manarchism" exist? Of course it does - the male rejection of feminist concerns and other sexist behaviors can be found in any ideologically-based movement for social change. However, in my experience manarchism is becoming a thing of the past, largely thanks to the educating work of anarcho-feminists and their sister eco-feminists. So yes, anarchism is inherently feminist, as it must be if it is true to itself. Is feminism inherently anarchist? Many would disagree but I believe it must be, for the same reasons anarchism is inherently feminist.