Or HaChaim on Genesis 29:12/אור החיים על בראשית כ״ט:י״ב

1 ויגד יעקב לרחל כי כי אחי אביה הוא, Jacob told Rachel that he was her father's brother, etc. This means that Jacob told Rachel that his relationship to her was based on two elements. 1) There was a biological relationship, i.e. he was a blood relative of her father; 2) there was a spiritual relationship between them inasmuch as he was a son of Rebeccah who was known far and wide for her righteousness. Righteous people are considered as all related to one another.

2He may have hinted at something we learned in Megillah 13 where we are told that Rachel told Jacob that her father was a swindler. Jacob told Rachel that he could match her father since he was of the same family. Having said so Jacob became afraid that Rachel would form a bad impression of his character; he therefore added that he was the son of Rebeccah who had employed wiles only in order to help justice and righteousness to prevail. This is the deeper meaning of Kohelet 7,12 that "(applied) wisdom preserves the lives of its possessors." He would never employ trickery for nefarious purposes something that would result in the destruction of its perpetrators.