English does not have one widely used everyday kinship term meaning “your son-in-law’s parents.” In most situations, the clearest wording is simply “my son-in-law’s parents” or, from the daughter’s perspective, “my daughter’s in-laws.” A few other expressions work in particular contexts.
Clear Options by Context
- My son-in-law’s parents
- My daughter’s in-laws
- My daughter’s parents-in-law
- The parents of my son-in-law
- The groom’s parents
- The other set of parents
- Our children’s in-laws
- Co-in-laws
My son-in-law’s parents
The clearest and least ambiguous expression. It works in almost any context. Example: We’re having dinner with my son-in-law’s parents this weekend.
My daughter’s in-laws
Natural when the relationship is being described through your daughter. Example: My daughter’s in-laws are visiting for the holidays.
My daughter’s parents-in-law
Grammatically standard, though “in-laws” is more common in everyday speech. Example: We met my daughter’s parents-in-law before the wedding.
The parents of my son-in-law
A more formal or explicit version of the same relationship. Example: The parents of my son-in-law live in another state.
The groom’s parents
Clear in a wedding context when your daughter is the bride. Example: We met the groom’s parents at the rehearsal dinner.
The other set of parents
An informal contextual phrase when everyone already knows which couple or family you mean. Example: The other set of parents is arriving on Friday.
Our children’s in-laws
Can work when two sets of parents are describing their relationship through a married couple, though it is not a fixed kinship term. Example: We see our children’s in-laws a few times each year.
Co-in-laws
A real but uncommon term sometimes used for the parents of one’s child’s spouse. Many English speakers will not recognize it, so it is usually better to explain the relationship. Example: The two families are technically co-in-laws, although we normally just use each other’s names.
Is There a Standard Word?
Not in ordinary modern English. “Co-in-law” appears in dictionaries and reference works in some varieties of English, but it is far less familiar than terms such as mother-in-law or brother-in-law. Using it without explanation may confuse readers.
For most conversations, “my son-in-law’s parents” is the best choice because it is immediately clear and does not invent a relationship label that the listener may not know.