As someone says There is a woman or a child hidden in every man…
I still think selfish is a big word to use here.
I say love both. Ok to love more your own parents but do not have to either show it so openly and be a bit diplomatic or least one can do is not to hate or despise them. Trust me there are in-laws who love their DIL a lot and fight for their rights with their husbands.
I am making both husband and wife responsible here to love their respective in-laws.