It is possible, if they both selected "someone else can claim me as a dependent on their return," which releases their dependency exemption. Otherwise your e-filed return will get rejected.
Here are the 7 test for claiming a dependent:
1) You provided more than half
of their financial support. More info
2) They made less than $4,050 in gross income
during 2016 unless they are a
qualifying child (under 19 OR a full time student under 24
OR permanently disabled)
3) They live with you or they are related to
you.
4) They are a U.S. citizen, resident alien,
national, or a Canadian or Mexican resident.
5) They aren't (or won't be) claimed as a
dependent by someone else.
6) They aren’t filing a joint return with
their spouse.
7) You are not being claimed as a dependent on
someone else's return.
