Here the first use of the word "they" as well as the words "their" and "them" refer to Paul and Silas. Compare [Acts 16:25](./25.md). The last use of the word "they" refers to the people in the jailers' household.
This can be stated in active form. AT: "Paul and Silas baptized the jailer and all the members of his household" (See: [[rc://en/ta/man/translate/figs-activepassive]])