Near the end of the birchat hamazon there is wording for a sentence for eating at the table of one's parents. (See the left side of the quote below). That sentence refers to "them, their house, their family, and all that is theirs". But some people have only one living parent. Why is there no wording suitable for someone eating at the table of their widowed mother or widower father (i.e., in the singular)?
(Related but different question: Why no singular in birchat hamazon for "ours and all that is ours"?)