I am also looking for information regarding the Westerhoff's from The Netherlands. So far I have very little information except that my Grandfather, Andrew Westerhoff was probably born in the town of Warffum in The Netherlands. His wife, Hattie Rooze was born in 1892 in Warffum. I believe Andrew's father was Jacob but I have not substantiated this.
My father's name was Cornelius and he was born in Chicago in 1915. He had three brothers and two sisters. One sister died during childbirth.
If you wish more details about my uncles/aunts, please let me know and I'll be happy to share. I do have more information on the Rooze side of my ancestry.