La maison des Jackson est sur la gauche.

Question

hello madam/sir,I have a question why here they used 'des' instead of 'de'? As we use des for plural, but here nothing is plural.

Accepted Answer

Hi Noor, Maarten is absolutely correct: "les Smith" are "the Smiths" in English. In French it is understood as plural even though the family name is in singular:
Les Smith viennent nous rendre visite. -- The Smiths are coming to visit us.
The kwiziq lesson on this is here: Surnames don't pluralise (kwiziq.com)
Surnames don't pluralise

Answer

It is plural. Can’t find the lesson to link for you, but French always uses the surname in the singular, and the article changes to indicate plurality - for example, “les Jackson”  or “les Smith” whereas in English the article is the same, but the name is made plural eg to “the Jacksons” or “the Smiths” etc