My son had viral pink eye and eventually his sister got it. is it possible for him to get it from her again or not because it was viral?

Yes: Yes, could get the infection again, especially, if not totally resolved. Parents can also get this problem. Careful hand washing and separate hand towels can minimize spread.

Unlikely: Once your son has recovered from his pinkeye from whatever virus triggered it, he should have enough protective antibody floating around in his system to avoid a recurrence.If he has another bout it would likely be another agent, not the germ he shared with his sister.Even then, there is often a blocking agent called interferon that lingers in the area preventin new viral invasion for a while.