Hi Dano,
I learned most of this through relatives' research done in Scotland several decades ago (I understand it was meticulous, but the sources annoyingly do not survive). I have David Wilson's marriage to Agnes Easton as 20 Dec 1850, and her birth as 11 Jan 1824. My relatives, aforementioned, never bothered to write down her parents' names if they found them.
I'm now trying to replicate it for posterity with better attention to detail. David and Agnes Wilson are found in 1861 in E. Shieldhill with children James, 12, Peter, 9, Jane, 8, David, 6, and John, 3. I have David Wilson, b. 22 Jul 1855 in Shieldhill, who emigrated to Iowa in 1880 with his older brother Peter. What I do know is the U.S. side. Based on the date of their immigration listed on later censuses, and their ages, they are the <a href="
http://www.castlegarden.org/quick_search_result.php?p_first_name=David&p_last_name=Wilson&m_arrival_date_start=1870&m_arrival_date_end=1890&co_id=7&o_id=MNR&m_id=35683&submit.x=15&submit.y=18">David </a>and <a href="
http://www.castlegarden.org/quick_search_result.php?p_first_name=Peter&p_last_name=Wilson&m_arrival_date_start=1870&m_arrival_date_end=1890&co_id=7&o_id=MNR&m_id=35683&submit.x=0&submit.y=0">Peter Wilson</a> (both listed as 'Miner', who arrived in New York City on the Bolivia on 1 June 1880. They managed to get enumerated in the 1880 census <a href="
http://www.familysearch.org/Eng/Search/frameset_search.asp?PAGE=census/search_census.asp">while being processed at immigration</a>. Their mother came a year later according to her later census records, but I haven't found a ship manifest.
In the U.S., David married Margaret Aitken (b. Harthill, 10 Aug 1864, I do not know which Harthill, these notes are not specific) on 19 Apr 1887 in Sigourney, Keokuk County, Iowa. I know nothing further on Peter from the family, and think he didn't start one in the U.S. He appears in one census, 1900, living in What Cheer in Keokuk County with his mother. David and Margaret moved to Bussey in Marion County and had four children, Anna b. Dec 1886, David b. Jan 1884, Thomas b. Feb 1891, and Agnes b. Mar. 1895. Most descendants are still in Bussey, Iowa - I have more details if you're interested in a fuller descent from David, but they may be irrelevant for the board.
Incidentally, I notice in your sig that you are also researching the Waddell surname. I have no connection in that one to any specific place, merely a Mary W. Waddell who shows up suddenly somewhere between North Carolina and Iowa sometime in the 1850s - very briefly - (unrelated to Wilsons except by common ancestry of me), but I thought I'd mention her.
This seems to be an extremely active and helpful community. I'll definitely be sticking around
-satyadasa