Fe4 in this case can not be equally considered as the manga or fe5 because of the way it works: It doesn't take into account the relationships of the characters until just the last chapter and is prepared for any couple that migth happen, thus cannot be considered too much canon(in my opinion) when talking about the heritage.
For example, the AideenXJamka relationship began in the manga as soon as he joined the army, while in my latest playthrough it never happened and the only dialogue with her pairing was at chapter 5. Also to note that Leif can only be borned before Ced because Cuan's pairing is pre-determined, while Erin can fall in love in the last turn of the chapter having the same consequences as if it didn`r happen. The manga and fe5 show another version that doesn't depend on the player, and thus the story can be analysed more seriously.
