Can we use isomil milk formula in infants with milk allergic parents?

Yes. With both parents allergic isomil is an alternative. Thee are others and you mau want to talk with your pediatrician.
Makes no sense. Feeding an infant soy formula just because his/her parent (s) has milk protein allergy is senseless. If infant develops symptoms and signs of milk allergy, formula made of protein hydrolysate, i.e., alimentum or neutramigen, is generally recommended.