Destiny, sometimes referred to as fate (from Latin fatum – destiny), is a predetermined course of events. It may be conceived as a predetermined future, whether in general or of an individual.
Allah says in the Quran that no one will bear the burden of another. We are all responsible for our deeds.
It is not healthy to go through life with a sense of pre-destination that one will go to hell, because that can easily become a self-fulfilling prophecy.
Sometimes some people are irresponsible when they talk about illegitimate children and either say things without thinking, or else they don't critically examine the texts they are talking about and quote them without thinking or comparing or examining them closely. It perhaps doesn't occur to them that some of the people sitting there listening are not of legitimate birth. There should be more responsibility in discussing these things so that people do not go around worrying they will go to hell because of what their forebears did.
In Usul al-Kafi Vol. 1 (available from WOFIS in Iran), Imam 'Ali (as) explains that the decree is not finalised until the actual moment that it is brought into existence. Up until that time, there is room for the decree to be changed, or withheld. It is a key teaching from the Ahl al-Bayt (as) that you can have a living and dynamic relationship with Allah (swt) and that du'a, as well as other actions, can alter what is decreed. I know of the expression in the Middle East where they say 'the name of your spouse is written on your forehead', which sounds like an unchangeable destiny, but through du'a you may change that name.
Yes. Du'a can change many things in our life and make it much better. Du'a can make you marry a better person and can make your life happier. Many destined things can be changed by Du'a and good deeds or can be worsened by bad deeds.
Tablet of Destiny اللوح المحفوظ (Al-Lawh Al-Mahfoodh) has what Allah The Glorious Has written for us which is unchangeable like our parents, relatives, tribe, place of birth, color of eyes and skin etc.
Such matters in our life are fixed in the Tablet of Destiny (Al-Lawh Al-Mahfoodh) but it does not make any change nor effect on us on the Day of Judgment.
Our life span, our income, our health can be changed according to our deeds, as all are in the (Tablet of Mahw and Ithbaat) (omitting or confirming). This tablet is not Al-Lawh Al-Mahfoodh which is unchangeable.