Why does my family talk bad about my deceased father?

my father died of cancer back in 2016

many years ago i heard my father cheated on my mom & was a big drinker i dotn remeber that my dad & mom broke up in 2003 or 2004.

me my sister & mom went out to dinner.

when her & my mom were along she my sister said to my father i was out of it.

my mom said he is sad about his dead my sister then said my father never did much for me.

my mom & sister put my dad down a lot i don' like

he did a lot for me

Why does my family talk bad about my deceased father?
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