How to evict someone who moved in relatives

[Deb Doerr]

Our new tenant moved in one of our triplexes and the day she moved in, sent us a text asking if her son and his girlfriend who is expecting a baby in a few months, could move in for a few weeks. My husband specifically put in the lease that no additional people could move in without consent. We said no and suggested other apartment complexes in the area that had available units. She said "ok". We know they moved in with a child. How do I prove it if I want to give her a 30 day notice. She just moved in the end of August.