No, each ‘wireless’ system tends to be incompatible with another, certainly other companies wireless speakers cannot be connected to Sonos. There’s one slight caveat, Sonos does offer connection to Google Voice and Amazon Voice systems, which can offer some interoperability, but those ‘smart speakers’ do not connect directly to the Sonos signal. 

Not directly as you would another Sonos.

You could use a Port to feed sound, using a wire, to your other speakers, how well it would sound is questionable.