What relationship is my sons wife's sister?

[Marcariel]

There is a relationship question in an app (on Facebook) that won't allow me to add her, or accept her as a relative, without a relationship. Is there a formal relationship title for this person? Does the app need to update it's relationship choices .. or let me list her simply as an in-law?

[Sir Viever]

I don't think there is. The name "daughter-in-law" is the only title that has a person in the situation. The daughter-in-law's sister would be "sister-in-law" to your son, but I don't think there's a title that relates specifically to you. Not sure.

[Kelcy]

I do not think that there is a formal title for that relationship,seems like that is to distant to count.