Judges 8:30

And Gideon had seventy sons of his body begotten ,.... Not after his victories, for it is plain he had children before; mention is made of Jether, his firstborn, as a youth able to draw a sword, and slay with it, Judges 8:20 but this was the number of all his sons, both before and after, and a large number it was; and the phrase "of his body begotten", or "that went out of his thigh" is used to show that they were his own sons, begotten in wedlock, and not sons that he had taken into his family by adoption, or that he was father-in-law to, having married a woman or women that had sons by a former husband; but these were all his own:

for he had many wives ; which, though not agreeable to the original law of marriage, was customary in those times, and even with good men, and was connived at; and this is a reason accounting for his having so many sons.