How Do You Treat a Change in "Roommates" - Really a Change in Couple Partners?

[Burt L.]

BP Nation- I signed a lease with a couple six months ago and since then the fellow developed a monogomy problem - I used to  live next door. There is a new boyfriend presented as a new roommate and what happens behind closed doors is not at issue. 

I let the gal know the fellow would need to fill out an application so I could have his info. I checked at TLO and no liens, etc but no background check done. I think I should at a minimum ask to approve a background check as well. The security deposit issue will need to be worked out amongst the renters. 

The fellow also has two dogs and I've always had a one-dog maximum, or with a fourplex I shortly will have 8 dogs. These pets are a 10 year old Collie-mix and an 8 year old Hound-mix; not really sure what that is. The gal had an older dog but had to put him down a month ago or so. I should probably call his landlord, even though I'm in the middle of a year's lease and didn't think I'd  be doing such screening. I had to "exit" a previous renter in the same  unit for having a very aggressive dog - the pets can be worse than the people, though they are usually similar. I have since met the pets beforehand but that renter came from out-of-state. I don't really want to turn the unit and probably can't legally, if an original tenant remains. 

I think I don't I want to put this potential new resident on the lease, as if she should leave, then I get whoever he might find next and I've strayed further and further from my initial screens.  

I wanted to see what I"m missing here - thank you.