Have you read The Left Hand of Darkness? You should, it's very good. Also will explain dwarf biology in detail. The TL;DR is that dwarves are asexual most of the time and only express sexual characteristics in their fertile periods; whether they express male or female is a coin flip each time. They do not have gendered words and barely understand other races' obsession with sex and its related complications. When speaking, they often get confused by gendered pronouns and may mix them up even in one sentence.
They do form partnerships, which can only be sworn once; vows may be broken in rare circumstances, but a partnership can't ever be sworn with a new dwarf afterwards. Mating isn't really considered a necessary part of these vows, and children of one partnership may have many different biological parents. "Child of the Flesh" is a dwarf's child who was born from their own body, and "Child of the Heart" is a child that was born to their partner.