Florida State University sociologist Kathryn Harker Tillman analyzed data from a nationally representative study of more than 11,000 U.S. adolescents in grades 7 through 12.

Teens in the most complicated family arrangement of all -- those with both half- and step siblings -- like the 1968 movie "Yours, Mine and Ours" remade in 2005 -- fared better than those who live with only step-siblings or only half-siblings. Tillman theorized that the parents' decision in these more complicated families to have a biological child together may reflect a stable relationship.

The study, published in the journal Social Science Research, found boys living with half- or step-siblings appear to have the hardest time coping, with average GPAs one-quarter of a letter grade lower than boys who live with only full siblings.

Girls with half- or step-siblings also had lower GPAs than those living with only full siblings, but the difference was much smaller. Boys and girls in these types of families also had more school behavioral problems, such as trouble paying attention, getting homework done and getting along with teachers and other students.