Just because a Mrs Cirdan isn't mentioned doesn't mean she definitely didn't exist though. Mrs Thranduil isn't mentioned but she must have existed. Since Tolkien says that marriage early in life was the norm for elves, there celarly wasn't the imbalance in the genders as occurred with dwarves - though if you look at the extant elvish geanealogies you would think that the gender imbalance was even greater among elves than the dwarves ..... alas for the unwritten history of women ....
As for kinship - the Valar were unborn yet were still regarded as having siblings who were coeval in spirit. It is not impossible that a similar attitude was taken with the first elves...