Nested possessives

Let's imagine the following situation:

My mom has a boyfriend and her boyfriend has a car.

I borrowed this car and I want to tell another person who is the owner of this car, I believe I have to use 's twice in this sentence:

This is my mom's boyfriend's car.

Honestly I think that this is correct, but I am unsure if I can use the 's twice or more in this sentence, is this correct? Could I go even further than that?

This is my mom's boyfriend's brother's car.

Thanks a lot!

Answer

Yep, it works fine.

1. 
   

   
   

   my mom

   
   

   
   

   This is a noun phrase (NP). The head is mom, and its determiner is my.

   
   

   
   

   [my mom]'s

   
   

   
   

   We've added the genitive 's, so now it's a genitive noun phrase. Genitive NPs can be determiners in larger noun phrases:

   
   



2. 
   

   
   

   [my mom]'s boyfriend

   
   

   
   

   Now we've made a larger NP. Its determiner is the genitive NP [my mom]'s, which we made in step one.

   
   

   
   

   [[my mom]'s boyfriend]'s

   
   

   
   

   Now we've added the genitive 's again, so we've got a genitive NP again.

   
   



3. 
   

   
   

   [[my mom]'s boyfriend]'s brother

   
   

   
   

   This whole thing is an NP. Its determiner is the genitive NP [[my mom]'s boyfriend]'s.

   
   

   
   

   [[[my mom]'s boyfriend]'s brother]'s

   
   

   
   

   Now we've made it into a genitive NP. Again.

   
   



4. 
   

   
   

   [[[my mom]'s boyfriend]'s brother]'s car

   
   

   
   

   This is another NP. Its determiner is the genitive NP [[[my mom]'s boyfriend]'s brother]'s.

   
   

As you can see, we're repeating the same operations over and over. You can do it as much as you like. Eventually you'll probably amuse or confuse your conversation partner, though.