Nicknames

We have some randowm nicknames in our home. Emma has gone by Bozemma. We call Addie Pax or Paxie since Emma called her that when she was just a few months old. Titus has had a long list of names from his sisters: Brick, Tuna, Big Son, and the enfamous Mr Baroski. And now it is Bog Son's turn. He has given both the twins their own nicknames. He calls Nehemiah, Miah (which is normal). However what is not so normal is Gwenyth's nickname. He has called her Den or Denny since she was born. He can't pronounce G's, so instead of calling her Gwen or Gwenie, he calls her, Denny...and now so do the rest of us. Yesterday, I thought I would try to work on the pronunciation of his sister's name.
I tried to get him to "Guh" like a G sound.
"Guh, guh, guh."
Titus gave no reply.
I said can you say, "guh, as in Guh-wen?"
His reply, "Den."
I said, "No, Guh. Guh-wenyth. Can you say that?"
Titus: "Denny."
Me: "GWEN."
Titus: "Denny."
Then I tried a different strategy and decided to emphasize the "-th" at the end.
I said "gwenyTH. -TH can you try that?"
Titus: "Denny-th."

That was good enough practice for one day. We'll end on "Dennyth." The funny thing is she responds to Denny. Not an attractive name, but it is her nickname for now.