First task solution
Task1: Months are keys of dictionary
Task2: PEP8 check , no more absent or additional whitespaces
Task2: Cache to work with *args
Task2: return list not set with children
Task3 : set default value for father and mother
Task3: new method finding siblings by gender
Task3 : use list of successors instead of set
Task3: use self
Task4: use constants