As I said before not much can be explained if one takes these stories at there face values. Let us take the story of Dronacharya. He was born when sperms were dropped in a 'drona' - a container made out of dry leaves. He was main teacher of Pandawas and Kaurawas. He was married and had a son . , Ashawathhama . Per our our understanding he is immortal . Drona was friends with Drupada. Drupada became king of Panchala. When Drona asked him for favors, cows etc , Drupada refused, .Drona asked Pandawas to help and they defeated drupada. Drona then allow Drupada to retain 'southern half ' of the kingdom but not the northern half . So Drupada decided to do tapa and 'Yadnya ' . He was blessed with a son which came out of sacrificial fire . He was the Senapati --named Drishtadyumna. Now how do you make any sense out of this ?
Drona represents stored up karma or their lasting impression . let me explain , I call it circle of mind . Lets say ,I am offered slice of pizza , and I have never seen pizza nor tested it . I will have no reaction to it . i/e. I will neither feel like eating it or not eating it . But then you say that it's good , so I try it . and I like it ( or dislike it ) . So next time I am hungry I may think of eating pizza or if i see pizza I will have desire to eat it . Again if I eat it it will solidify my impression . S o my 'action ' of eating pizza leads to an 'impression ' -good or bad - bad- that leads to desire which in turn leads to action and so on so forth. These lasting impressions are stored in Astral body at death and after death when you are reborn they direct our actions . So they 'guide' us or 'teach' us . So these SAUNSKARAS are what is Dronacharya .Since we do not stop action and continue to have desires these are immortal . So the son of Drona is immortal. These desires can not be destroyed easily . and they will demand favors from time to time . You will have to 'fight ' with them . This is the fight between Drona and Drupada. In this fight when one looses , he may still have 'control ' over 'southern part of the kingdom '( body is kingdom and southern part is lower centers .) Then one can further meditate and do sacrifice ( yadnya) and it will give the son that will destroy stored up desires--Drona . So this symbolism explains Drona teaching both Pandawas and Kaurawas --the desires and their impressions are directing our good and bad actions. Also why Ashawathhama is immortal and why Drrishtadyumna is mentioned in verse 3 of 1st chapter of Geeta, as leading Pandawas' army.