On most bookings a cleaner works alone. A standard flat cleaning is planned for one person and paid for one person, so there is no point in two of you turning up.
The exceptions are large sites: post-renovation jobs, big houses, offices and clean-ups after events. Those are handled by a team of two to four people, and working in a pair there is entirely realistic. Tell the manager you would like to be on the same shift as a particular person, and you will be scheduled together where possible.
The second option is that both of you sign up as cleaners and take bookings in the same district. You travel separately but to nearby addresses, which is convenient if you share one car.
Bringing along someone who is not employed by the company is not allowed. The insurance fund and the guarantee only cover registered staff, and the client must know exactly who is in their home.