Is having flat feet genetic?

Yes. Yes, flat feet or per planus can be genetic, but could result from trauma. Trauma induced flatfeet usually is unilateral, while bilateral flatfeet is genetic.
Depends. Pes planus can be a result of genetic factors, joint laxity, anatomic variances and posterior tibial tendon degeneration (adult-acquired flat feet).
Yes. Flat feet is genetic because the shape of a person's body, including his feet, is inherited from his parents through the genes. People with flat feet often have relatives with flat feet.