Can you do a twin study if your children are fraternal twins?

Probably yes!: Twin studies are occuring all over the place and are much needed! there are different kinds of twins and you may need to ask the study investigators if you can be included in their specific study.

Not Usually: Normally twin research studies like to study identical twins because the genetics are identical.

Depends on issue: Fraternal studies are more relevant as studies of early childhood environment, rather than genetic influences. Any study can be valid if the target of that study is reasonable.