Yes, but that doesn't flow as well.
It's like putting the engine of a train behind the caboose. It would still work, but it is a little weird.
I translated as This is his mom's, and the program considered it incorrect. The program's correct answer is This is his mom. I think it could be both, depending on context. For instance, if you are pointing to an object (feminine) and says the phrase, my translation would be correct, no?mean