Many languages distinguish between inclusive and exclusive first-person plural pronouns (“we”). (Click or tap here to see more details)
The inclusive “we” specifically includes the addressee (“you and I and possibly others”), while the exclusive “we” specifically excludes the addressee (“he/she/they and I, but not you”). This grammatical distinction is called “clusivity.” While Semitic languages such as Hebrew or most Indo-European languages such as Greek or English do not make that distinction, translators of languages with that distinction have to make a choice every time they encounter “we” or a form thereof (in English: “we,” “our,” or “us”).
For this verse, translators typically select the exclusive form referring to only Paul.
Source: Velma Pickett and Florence Cowan in Notes on Translation January 1962, p. 1ff.
Mal uses 4 forms of the first-person plural pronoun: inclusive dual “we” (includes the person that the speaker addresses), exclusive dual “we” (includes the speaker plus another person but excludes the person that the speaker addresses), inclusive plural “we” (includes all persons that the speaker addresses), exclusive plural “we” (includes the speaker plus at least two other persons but excludes the other persons person that the speaker addresses).
In this verse the Mal translation is using the exclusive dual form, which includes Timothy (see verse 1:1) but excludes all addressees.
Source: David Filbeck in The Bible Translator 1994, p. 401ff.