Jacob actually served Laban for a total of 20 years, 31:38. He marries Leah and Rachel only one week apart. Assuming that Leah got pregnant following her first menstrual cycle after they were married, then Ruben is born in their first of marriage. Joseph is born six years later. Let's look at the math. After seven initial years of service, Jacob marries both women. Ruben is born in the first year of their marriage, this makes eight years. Joseph is born six years later. This places Jacob in Pandan-arim 14 years. He continues to serve Laben for another six years. This makes Joseph six hears old when they leave Pandan-aram.
Simeon - 2nd years
Levi - 3rd year
Judah- 4th year
then stop having children-say 5th year
Issachar- 6th year
*Zebulun-7th year, not to mentioned Dinah