I believe this is correct. I installed this mod hoping to adopt a stray cat that was on my lot. Previously a pop-up told i couldn't have more than 6 pets on one lot. After the mod it told me i couldn't have more than 8 family members on one lot...
Current family has: one elder, two adults, one baby, two dogs (one pregnant, i think 3 puppies) and one cat.

Hacks installed (not sure if you want this info): No friends needed, Perfect plants, college adjuster, Triplet hack, and this one. All the above hacks are said to be compatible by Twojeffs himself.