After fully hearing the charges or complaints and hearing all witnesses produced by the board and the person against whom the charges are pending, and after full, impartial and unbiased consideration thereof, the board of school directors shall by a two-thirds vote of all the members thereof, to be recorded by roll call, determine whether such charges or complaints have been sustained and whether the evidence substantiates such charges and complaints, and if so determined shall discharge such professional employe. If less than two-thirds of all of the members of the board vote in favor of discharge, the professional employe shall be retained and the complaint shall be dismissed.

No member of any board of school directors shall vote on any roll call if he is related as father, mother, brother, sister, husband, wife, son, daughter, stepson, stepdaughter, grandchild, nephew, niece, first cousin, sister-in-law, brother-in-law, uncle or aunt to the professional employe involved or to any of the parties instituting the complaint.