Found the reference to William's marriage record, from Marion, but it's from quite a few years ago. I hope you can talk to her, as I think she had NOT at that time identified the correct William and Mary.
Then see this family tree, for William Lowe married to Mary Sanderlin - and married on the above date and place - BUT they are NOT shown as parents to YOUR David! http://esoteric.stormloader.com/fam/d75.htm#P1414http://esoteric.stormloader.com/fam/d75.htm#P1414
Therein lies the problem with using online family trees.
I forget where did you get David's middle initial of "H" from?
"Your" William Lowe is mentioned in this book: History of Green County [Wisconsin], published 1884 "In 1849 the town of Mount Pleasant was divided into five districts.The officers of the various districts at that time were as follows: No.1.--Thomas Fenton, director: Aranthus Thomas, treasurer; Ephraim Moody, clerk.No.2.--Amos Perry, director; James Bedell, treasurer; Lyman Wright, clerk.No.3.--Henry Adams, director; A.F. Steadman, treasurer; John Manly, clerk.No.4.--William Lowe, director; A.P. Jewell, treasurer; William Boyls, clerk.No.5.--Benjamin Rima, director; Joseph Conklin, treasurer; David McKee, clerk.James L. Powell was town superintendent of schools.On the 1st of September, 1849, the reports of the district clerks show that there were 210 scholars in the town.At that time districts Nos.1 and 4 had log school houses; 2 and 5 stone school houses, and No. 3 was without a house." http://www.monticellowi.com/GreenCo/mtpleasanthistory.htmhttp://www.monticellowi.com/GreenCo/mtpleasanthistory.htm
In one of the many posts by your cousin Marion - our angel - she mentions a Lowe DNA project. A male descended from a male descended from a male descended from William might be helpful to have in the project: http://genforum.genealogy.com/lowe/messages/5438.htmlhttp://genforum.genealogy.com/lowe/messages/5438.html