What is the ruling on adding paternal and maternal female cousins on Facebook with the intention of maintaining family ties, given that they appear wearing the hijab, and is this considered unlawful mixing?

Adding your female relatives on Facebook is not considered an impermissible mixing (ikhtilat), but it is unnecessary and there is a concern that it could be a pretext for unlawful communication, even though maintaining ties of kinship with paternal and maternal cousins is not obligatory and can be achieved through other means.