I found a comprehensive tree on the Biggar family by googling "Samuel Bigger and Agnes Montgomery". I wish I could send you the link but the best I can do is this which may or may not bring it up but googling should.
Another link is http://boards.ancestry.com/surnames.caruth/184.108.40.206.1.1/mb.as...
but the info is slightly different. I was wanting this particular Samuel's parents and the first site has his parents as Matthew Biggar married to Letitia Biggar whereas the second site has Joseph as his father. Personally, I think his father was Matthew. Who are you trying to tie in to the Bigger family?