Answer: The Bible does not directly state how old Jacob was when he wed the women who would build the nation of Israel. That said, it only takes piecing together a few well-known events and the chronology attached to them to determine how old he was when he married.
What the Bible reveals
Joseph, the first son of Jacob through his beloved Rachel, was sold into slavery by his brothers at the tender age of seventeen (Genesis 37:1 - 2). After thirteen years of various trials and troubles, he correctly interprets Pharaoh's dream as symbolizing seven years of bountiful harvests followed by seven years of famine (41:1 - 36). At the age of thirty, he is elevated to the second most powerful position in Egypt (verses 39 - 46).
It is after seven years of plentiful harvests and two years of famine (Genesis 45:1 - 6) that Jacob finally decides to leave Canaan. He takes his entire sixty-six member family and migrates to Egypt (Genesis 46). Once in Egypt he reunites with Joseph and is introduced to Pharaoh. Upon meeting the Egyptian ruler, the elderly Biblical patriarch reveals he is 130 years old (Genesis 47:7 - 9).
We can therefore deduce that Joseph was 39 years old (7 years of abundance plus 2 years of famine) when he reunited with his father. This means that Jacob was 91 (130 - 39) when Joseph was born!
Working for wives
When Jacob first met Laban (his mother's brother), he immediately fell in love with his younger daughter Rachel. Since he did not have the money to pay the bride price (the mohar) for her, he agreed to work seven years for him and then marry Rachel. After seven years, when it was finally time to become husband and wife, Laban tricked him into marrying his older daughter Leah instead (Genesis 29:16 - 26)!
Laban's response to the understandable anger directed at himself was to allow him to marry Rachel a week later. The catch was that he had to promise to labor another seven years as payment for Rachel (Genesis 29:25 - 30)! Joseph, the Bible reveals, was born at the end of this second seven-year period (Genesis 30:25 - 26).
With this further insight we can determine that Jacob was 84 years old (91 - 7) when he made both Leah and Rachel his wife. We also now know he was 77 (91 - 14) when he first met Laban and agreed to work for the right to wed.
A unique man
Jacob's advanced age when he wed was quite rare not only in his own time but also when compared to other generations born after Noah's flood. His twin brother Esau was forty when he married (Genesis 26:34) as was their father Isaac (25:20).
The age the ancestors of Jacob married (excluding his father) is not recorded in Scripture. What is revealed, however, is how old they were when they produced their firstborn son (Genesis 11). The first eight generations of his ancestors born after the flood (Arphaxad to Terah, who was the father of Abraham) had their first son at an average age of 36! If we exclude Terah, who had his first boy at 70, the average drops to slightly above 31 years old.