A correspondent writes to tell me about an argument at a cocktail party recently. Evidently there was a NY Times wedding announcement stating: 'Jane is the daughter of Mr. & Mrs. Jones of ...', and somebody was arguing that this would be an improper usage if the Jones's had more that one daughter. My correspondent argued that it wasn't necessarily so: ' Something about the special nature of the announcement suggests that to me. Any thoughts on the "right" answer?'
I think my correspondent is right: context is everything, when it comes to the use of the definite article. There are occasions when the usage the daughter would be misleading, if the parents had more than one daughter. If I say 'I'm going out with the daughter of Mr and Mrs Jones', it does suggest that the Jones's have only one, and if you knew that they had more than one you would be well within your linguistic rights to pick me up on it: 'Which one?' A more appropriate sentence would be 'I'm going out with one of Mr and Mrs Jones's daughters'. When the situation allows a choice between one and more than one, then the regular distinction between the and a applies.
But this is a wedding announcement, where the focus is on this particular bride, and nobody is thinking of the other twelve daughters that are in the Jones household. It is a fact that she is 'the daughter of Mr and Mrs Jones'. And here, at her wedding, she is the daughter, indeed, who they must be feeling very proud of. There is no choice between one and more than one here. So there is no ambiguity.
In any case, what would be the alternative? 'Jane is a daughter of Mr. & Mrs. Jones'? That sounds to me as if she's being given away rather casually. Of course, one could always avoid the issue altogether: 'Jane, daughter of....
There is probably a larger linguistic issue here, to do with the way articles are used with family members. I just asked my wife who she was, in relation to her mother. She said: 'I'm the daughter of Audrey Norman'. She is the only daughter. I then asked her about her brother Martin's relationship to her mother, and she said: 'He's the son of Audrey Norman'. But she has two brothers. Family members seem to ask for definite treatment, regardless of how many they are. 'Come and meet John. He's the uncle of Jane'. How many uncles has Jane got? We don't know. Nor do we know in the more natural 'He's Jane's uncle'.
I wonder if the usage developed early in kinship language as an extension from those family members who are necessarily unique - the mother, the father, the mother-in-law, the father-in-law - and where sentences such as 'Let me introduce you to a mother of Jane' are definitely anomalous!