Grandpa (Thomas Schell, Sr. aka The Renter) Timeline & Summary

In a series of letters that Grandpa wrote to his son, Thomas (Oskar's dad), but never sent, we learn about Grandpa's life.
Like Grandma, he grew up in Dresden, Germany, and lost his whole family when the city was bombed.
He moved to New York, but unable to get over the loss of his love, Anna, who was pregnant with their child, he loses the ability to speak.
He tattoos YES and NO on his palms to communicate, and writes everything down in a notebook.
One day he meets Anna's sister, and they marry, even though he doesn't love her.
When she gets pregnant with Thomas Jr., he's unable to deal with it, and he goes back to Germany.
He returns, but his son dies in the September 11 attacks before he gets to know him.
He moves back in with his wife, and helps his grandson dig up Thomas Jr.'s empty grave, but never tells Oskar that he's his grandfather.
Grandpa decides to leave Grandma again, but she follows him to the airport and they decide to live there instead. (Bathing in public restrooms and feeding on Dunkin Donuts, we guess…)