Abimelech, a son of Gideon and one of the seventy sons of Gideon, spoke to the members of his mother’s family, saying,

“Please speak in the hearing of all the men of Shechem: ‘Which is better for you, that all seventy of the sons of Jerubbaal reign over you, or that one reign over you?’ Remember that I am your own flesh and bone” (Judges 9.2).

If seventy, a multiple of seven, has any significance in this passage and story, I cannot see it. Therefore, it appears to be an incidental reference to seven.