Gen.com, Ancestry trees, LDS IGI side, Geneanet trees, rootsweb trees... none of these are usable sources for pre-1700 profiles.
Scotland's People, land transaction records, wills, POMs for medieval time, sasines, poll tax roles, and the like are all good sources for the time period.
There has been some discussion that the William Wallace seal is not that of the "Braveheart" but of someone else and that "Braveheart" may not even have really existed. While there was likely an historical figure named William Wallace the truth of the man may not fit the heroic deeds of the poem.
See: Morton, Graeme. "The Most Efficacious Patriot: The Heritage of William Wallace in Nineteenth-Century Scotland." The Scottish Historical Review 77, no. 204 (1998): 224-51. Accessed November 11, 2020. http://www.jstor.org/stable/25530836.
(Morton is a lecturer at University of Edinburgh)
The poem is not considered to be serious history. It was likely written around 1478 about 200 years after the Battle of Stirling Bridge. It is a tribute to a folk hero which means the basis of the information is at best iffy. The text cites various historians throughout the last few centuries who questioned the accuracy of the Blind Harry poem. "Throughout the 19th century, historians of all kinds struggled to know what to make of Harry as their source. In the absence of certainty, it was often patriotism which sustained a reason to believe."
Blind Harry is said to have based his poem on a book by John Blair written in Latin. There is no proof the book ever existed and it was a common contrivance to claim a Latin text to give an aire of authority used by romantic writers of the time period.
There was another William Wallace of the time period. And he was a loyalist during the civil wars. Sir William Wallace, baronet of Craigie. The Wallace of Braveheart legend has been described by Joseph Bain as "scantily illustrated by historical records and has been obscured by Harry."
Also there is no historical evidence of his birth, his marriage, or any children. Just wanted to make that clear as well.