The English word 'king' is related to the word 'kin'. In (early) Anglo-Saxon England, one is of a kingly family, rather than it being the title of a monarch. Only later, when the kingdoms get Romanised, is the kingly title equated to the Roman 'rex', monarch. The idea that kingship belongs to a certain class within society (a kingly family) rather than a single person continues for a long time, however, which means that by the time of the Viking expeditions in the 9th and 10th century it is still possible that 'many kings' were killed in a single battle, for example. This system of family kingship also made it possible that there could be multiple co-rulers over a single kingdom, but also that there was also a king available, even if many are killed.

You also asked whether there were any queens. The idea that a queen is a separate political entity distinct from the king does not seem to be something relevant to the Anglo-Saxon period. While some women could be monarchs or rulers (like Boudicca in the early Roman period, or Æthelflæd of Mercia in the 10th century) they do not seem to be appreciated as kings in their own right, so probably also not 'of the royal kin'. But at the same time, these women were respected as placeholders/caretakers of their husbands, and could definitely inherit property, including political office. This is entirely in line with how the distinction between masculinity/femininity was seen in this period: biological women could, in certain circumstances, take up the male role, like Hervor from the Edda, and be recognised as male to society, and thus worthy of rule, even if not of the kingly title.